Learning PHP(credit to w3 School) – PHP Advance Collection-1


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PHP Multidimensional Arrays

An array can also contain another array as a value, which in turn can hold other arrays as well. In such a way we can create two- or three-dimensional arrays:

Example

<?php
// A two-dimensional array:
$cars = array
(
array(“Volvo”,100,96),
array(“BMW”,60,59),
array(“Toyota”,110,100)
);
?>

Run example »


PHP – Multidimensional Arrays

A multidimensional array is an array containing one or more arrays.

In a multidimensional array, each element in the main array can also be an array. And each element in the sub-array can be an array, and so on.

Example

In this example we create a multidimensional array, with automatically assigned ID keys:

$families = array
(
“Griffin”=>array
(
“Peter”,
“Lois”,
“Megan”
),
“Quagmire”=>array
(
“Glenn”
),
“Brown”=>array
(
“Cleveland”,
“Loretta”,
“Junior”
)
);

The array above would look like this if written to the output:

Array
(
[Griffin] => Array
(
[0] => Peter
[1] => Lois
[2] => Megan
)
[Quagmire] => Array
(
[0] => Glenn
)
[Brown] => Array
(
[0] => Cleveland
[1] => Loretta
[2] => Junior
)
)

Example 2

Lets try displaying a single value from the array above:

echo “Is ” . $families[‘Griffin’][2] .
” a part of the Griffin family?”;

The code above will output:

Is Megan a part of the Griffin family?

PHP Date() Function

The PHP date() function is used to format a time and/or date.


The PHP Date() Function

The PHP date() function formats a timestamp to a more readable date and time.

Tip A timestamp is a sequence of characters, denoting the date and/or time at which a certain event occurred.

Syntax

date(format,timestamp)
Parameter Description
format Required. Specifies the format of the timestamp
timestamp Optional. Specifies a timestamp. Default is the current date and time

PHP Date() – Format the Date

The required format parameter in the date() function specifies how to format the date/time.

Here are some characters that can be used:

  • d – Represents the day of the month (01 to 31)
  • m – Represents a month (01 to 12)
  • Y – Represents a year (in four digits)

A list of all the characters that can be used in the format parameter, can be found in our PHP Date reference,date() function.

Other characters, like”/”, “.”, or “-” can also be inserted between the letters to add additional formatting:

<?php
echo date(“Y/m/d”) . “<br>”;
echo date(“Y.m.d”) . “<br>”;
echo date(“Y-m-d”);
?>

The output of the code above could be something like this:

2009/05/11
2009.05.11
2009-05-11

PHP Date() – Adding a Timestamp

The optional timestamp parameter in the date() function specifies a timestamp. If you do not specify a timestamp, the current date and time will be used.

The mktime() function returns the Unix timestamp for a date.

The Unix timestamp contains the number of seconds between the Unix Epoch (January 1 1970 00:00:00 GMT) and the time specified.

Syntax for mktime()

mktime(hour,minute,second,month,day,year,is_dst)

To go one day in the future we simply add one to the day argument of mktime():

<?php
$tomorrow = mktime(0,0,0,date(“m”),date(“d”)+1,date(“Y”));
echo “Tomorrow is “.date(“Y/m/d”, $tomorrow);
?>

The output of the code above could be something like this:

Tomorrow is 2009/05/12

Complete PHP Date Reference

For a complete reference of all date functions, go to our complete PHP Date Reference.

The reference contains a brief description, and examples of use, for each function!

PHP Include Files

PHP include and require Statements

In PHP, you can insert the content of one PHP file into another PHP file before the server executes it.

The include and require statements are used to insert useful codes written in other files, in the flow of execution.

Include and require are identical, except upon failure:

  • require will produce a fatal error (E_COMPILE_ERROR) and stop the script
  • include will only produce a warning (E_WARNING) and the script will continue

So, if you want the execution to go on and show users the output, even if the include file is missing, use include. Otherwise, in case of FrameWork, CMS or a complex PHP application coding, always use require to include a key file to the flow of execution. This will help avoid compromising your application’s security and integrity, just in-case one key file is accidentally missing.

Including files saves a lot of work. This means that you can create a standard header, footer, or menu file for all your web pages. Then, when the header needs to be updated, you can only update the header include file.

Syntax

include ‘filename‘;or

require ‘filename‘;


PHP include and require Statement

Basic Example

Assume that you have a standard header file, called “header.php”. To include the header file in a page, use include/require:

<html>
<body><?php include ‘header.php’; ?>
<h1>Welcome to my home page!</h1>
<p>Some text.</p>

</body>
</html>

Example 2

Assume we have a standard menu file that should be used on all pages.

“menu.php”:

echo ‘<a href=”/default.php”>Home</a>
<a href=”/tutorials.php”>Tutorials</a>
<a href=”/references.php”>References</a>
<a href=”/examples.php”>Examples</a>
<a href=”/about.php”>About Us</a>
<a href=”/contact.php”>Contact Us</a>’;

All pages in the Web site should include this menu file. Here is how it can be done:

<html>
<body><div>
<?php include ‘menu.php’; ?>
</div>

<h1>Welcome to my home page.</h1>
<p>Some text.</p>

</body>
</html>

Example 3

Assume we have an include file with some variables defined (“vars.php”):

<?php
$color=’red’;
$car=’BMW’;
?>

Then the variables can be used in the calling file:

<html>
<body><h1>Welcome to my home page.</h1>
<?php include ‘vars.php’;
echo “I have a $color $car”; // I have a red BMW
?>

</body>
</html>

PHP File Handling

The fopen() function is used to open files in PHP.


Opening a File

The fopen() function is used to open files in PHP.

The first parameter of this function contains the name of the file to be opened and the second parameter specifies in which mode the file should be opened:

<html>
<body><?php
$file=fopen(“welcome.txt”,”r”);
?>

</body>
</html>

The file may be opened in one of the following modes:

Modes Description
r Read only. Starts at the beginning of the file
r+ Read/Write. Starts at the beginning of the file
w Write only. Opens and clears the contents of file; or creates a new file if it doesn’t exist
w+ Read/Write. Opens and clears the contents of file; or creates a new file if it doesn’t exist
a Append. Opens and writes to the end of the file or creates a new file if it doesn’t exist
a+ Read/Append. Preserves file content by writing to the end of the file
x Write only. Creates a new file. Returns FALSE and an error if file already exists
x+ Read/Write. Creates a new file. Returns FALSE and an error if file already exists

Note: If the fopen() function is unable to open the specified file, it returns 0 (false).

Example

The following example generates a message if the fopen() function is unable to open the specified file:

<html>
<body><?php
$file=fopen(“welcome.txt”,”r”) or exit(“Unable to open file!”);
?>

</body>
</html>


Closing a File

The fclose() function is used to close an open file:

<?php
$file = fopen(“test.txt”,”r”);//some code to be executed

fclose($file);
?>


Check End-of-file

The feof() function checks if the “end-of-file” (EOF) has been reached.

The feof() function is useful for looping through data of unknown length.

Note: You cannot read from files opened in w, a, and x mode!

if (feof($file)) echo “End of file”;

Reading a File Line by Line

The fgets() function is used to read a single line from a file.

Note: After a call to this function the file pointer has moved to the next line.

Example

The example below reads a file line by line, until the end of file is reached:

<?php
$file = fopen(“welcome.txt”, “r”) or exit(“Unable to open file!”);
//Output a line of the file until the end is reached
while(!feof($file))
{
echo fgets($file). “<br>”;
}
fclose($file);
?>

Reading a File Character by Character

The fgetc() function is used to read a single character from a file.

Note: After a call to this function the file pointer moves to the next character.

Example

The example below reads a file character by character, until the end of file is reached:

<?php
$file=fopen(“welcome.txt”,”r”) or exit(“Unable to open file!”);
while (!feof($file))
{
echo fgetc($file);
}
fclose($file);
?>

PHP Filesystem Reference

For a full reference of the PHP filesystem functions, visit our PHP Filesystem Reference.

PHP File Upload

With PHP, it is possible to upload files to the server.


Create an Upload-File Form

To allow users to upload files from a form can be very useful.

Look at the following HTML form for uploading files:

<html>
<body><form action=”upload_file.php” method=”post”
enctype=”multipart/form-data”>
<label for=”file”>Filename:</label>
<input type=”file” name=”file” id=”file”><br>
<input type=”submit” name=”submit” value=”Submit”>
</form>

</body>
</html>

Notice the following about the HTML form above:

  • The enctype attribute of the <form> tag specifies which content-type to use when submitting the form. “multipart/form-data” is used when a form requires binary data, like the contents of a file, to be uploaded
  • The type=”file” attribute of the <input> tag specifies that the input should be processed as a file. For example, when viewed in a browser, there will be a browse-button next to the input field

Note: Allowing users to upload files is a big security risk. Only permit trusted users to perform file uploads.


Create The Upload Script

The “upload_file.php” file contains the code for uploading a file:

<?php
if ($_FILES[“file”][“error”] > 0)
{
echo “Error: ” . $_FILES[“file”][“error”] . “<br>”;
}
else
{
echo “Upload: ” . $_FILES[“file”][“name”] . “<br>”;
echo “Type: ” . $_FILES[“file”][“type”] . “<br>”;
echo “Size: ” . ($_FILES[“file”][“size”] / 1024) . ” kB<br>”;
echo “Stored in: ” . $_FILES[“file”][“tmp_name”];
}
?>

By using the global PHP $_FILES array you can upload files from a client computer to the remote server.

The first parameter is the form’s input name and the second index can be either “name”, “type”, “size”, “tmp_name” or “error”. Like this:

  • $_FILES[“file”][“name”] – the name of the uploaded file
  • $_FILES[“file”][“type”] – the type of the uploaded file
  • $_FILES[“file”][“size”] – the size in bytes of the uploaded file
  • $_FILES[“file”][“tmp_name”] – the name of the temporary copy of the file stored on the server
  • $_FILES[“file”][“error”] – the error code resulting from the file upload

This is a very simple way of uploading files. For security reasons, you should add restrictions on what the user is allowed to upload.


Restrictions on Upload

In this script we add some restrictions to the file upload. The user may upload .gif, .jpeg, and .png files; and the file size must be under 20 kB:

<?php
$allowedExts = array(“gif”, “jpeg”, “jpg”, “png”);
$temp = explode(“.”, $_FILES[“file”][“name”]);
$extension = end($temp);
if ((($_FILES[“file”][“type”] == “image/gif”)
|| ($_FILES[“file”][“type”] == “image/jpeg”)
|| ($_FILES[“file”][“type”] == “image/jpg”)
|| ($_FILES[“file”][“type”] == “image/pjpeg”)
|| ($_FILES[“file”][“type”] == “image/x-png”)
|| ($_FILES[“file”][“type”] == “image/png”))
&& ($_FILES[“file”][“size”] < 20000)
&& in_array($extension, $allowedExts))
{
if ($_FILES[“file”][“error”] > 0)
{
echo “Error: ” . $_FILES[“file”][“error”] . “<br>”;
}
else
{
echo “Upload: ” . $_FILES[“file”][“name”] . “<br>”;
echo “Type: ” . $_FILES[“file”][“type”] . “<br>”;
echo “Size: ” . ($_FILES[“file”][“size”] / 1024) . ” kB<br>”;
echo “Stored in: ” . $_FILES[“file”][“tmp_name”];
}
}
else
{
echo “Invalid file”;
}
?>

Saving the Uploaded File

The examples above create a temporary copy of the uploaded files in the PHP temp folder on the server.

The temporary copied files disappears when the script ends. To store the uploaded file we need to copy it to a different location:

<?php
$allowedExts = array(“gif”, “jpeg”, “jpg”, “png”);
$temp = explode(“.”, $_FILES[“file”][“name”]);
$extension = end($temp);
if ((($_FILES[“file”][“type”] == “image/gif”)
|| ($_FILES[“file”][“type”] == “image/jpeg”)
|| ($_FILES[“file”][“type”] == “image/jpg”)
|| ($_FILES[“file”][“type”] == “image/pjpeg”)
|| ($_FILES[“file”][“type”] == “image/x-png”)
|| ($_FILES[“file”][“type”] == “image/png”))
&& ($_FILES[“file”][“size”] < 20000)
&& in_array($extension, $allowedExts))
{
if ($_FILES[“file”][“error”] > 0)
{
echo “Return Code: ” . $_FILES[“file”][“error”] . “<br>”;
}
else
{
echo “Upload: ” . $_FILES[“file”][“name”] . “<br>”;
echo “Type: ” . $_FILES[“file”][“type”] . “<br>”;
echo “Size: ” . ($_FILES[“file”][“size”] / 1024) . ” kB<br>”;
echo “Temp file: ” . $_FILES[“file”][“tmp_name”] . “<br>”;if (file_exists(“upload/” . $_FILES[“file”][“name”]))
{
echo $_FILES[“file”][“name”] . ” already exists. “;
}
else
{
move_uploaded_file($_FILES[“file”][“tmp_name”],
“upload/” . $_FILES[“file”][“name”]);
echo “Stored in: ” . “upload/” . $_FILES[“file”][“name”];
}
}
}
else
{
echo “Invalid file”;
}
?>

The script above checks if the file already exists, if it does not, it copies the file to a folder called “upload”.

PHP Cookies

A cookie is often used to identify a user.


What is a Cookie?

A cookie is often used to identify a user. A cookie is a small file that the server embeds on the user’s computer. Each time the same computer requests a page with a browser, it will send the cookie too. With PHP, you can both create and retrieve cookie values.


How to Create a Cookie?

The setcookie() function is used to set a cookie.

Note: The setcookie() function must appear BEFORE the <html> tag.

Syntax

setcookie(name, value, expire, path, domain);

Example 1

In the example below, we will create a cookie named “user” and assign the value “Alex Porter” to it. We also specify that the cookie should expire after one hour:

<?php
setcookie(“user”, “Alex Porter”, time()+3600);
?><html>
…..

Note: The value of the cookie is automatically URLencoded when sending the cookie, and automatically decoded when received (to prevent URLencoding, use setrawcookie() instead).

Example 2

You can also set the expiration time of the cookie in another way. It may be easier than using seconds.

<?php
$expire=time()+60*60*24*30;
setcookie(“user”, “Alex Porter”, $expire);
?><html>
…..

In the example above the expiration time is set to a month (60 sec * 60 min * 24 hours * 30 days).


How to Retrieve a Cookie Value?

The PHP $_COOKIE variable is used to retrieve a cookie value.

In the example below, we retrieve the value of the cookie named “user” and display it on a page:

<?php
// Print a cookie
echo $_COOKIE[“user”];// A way to view all cookies
print_r($_COOKIE);
?>

In the following example we use the isset() function to find out if a cookie has been set:

<html>
<body><?php
if (isset($_COOKIE[“user”]))
echo “Welcome ” . $_COOKIE[“user”] . “!<br>”;
else
echo “Welcome guest!<br>”;
?>

</body>
</html>


How to Delete a Cookie?

When deleting a cookie you should assure that the expiration date is in the past.

Delete example:

<?php
// set the expiration date to one hour ago
setcookie(“user”, “”, time()-3600);
?>

What if a Browser Does NOT Support Cookies?

If your application deals with browsers that do not support cookies, you will have to use other methods to pass information from one page to another in your application. One method is to pass the data through forms (forms and user input are described earlier in this tutorial).

The form below passes the user input to “welcome.php” when the user clicks on the “Submit” button:

<html>
<body><form action=”welcome.php” method=”post”>
Name: <input type=”text” name=”name”>
Age: <input type=”text” name=”age”>
<input type=”submit”>
</form>

</body>
</html>

Retrieve the values in the “welcome.php” file like this:

<html>
<body>Welcome <?php echo $_POST[“name”]; ?>.<br>
You are <?php echo $_POST[“age”]; ?> years old.

</body>
</html>

PHP Sessions

A PHP session variable is used to store information about, or change settings for a user session. Session variables hold information about one single user, and are available to all pages in one application.


PHP Session Variables

When you are working with an application, you open it, do some changes and then you close it. This is much like a Session. The computer knows who you are. It knows when you start the application and when you end. But on the internet there is one problem: the web server does not know who you are and what you do because the HTTP address doesn’t maintain state.

A PHP session solves this problem by allowing you to store user information on the server for later use (i.e. username, shopping items, etc). However, session information is temporary and will be deleted after the user has left the website. If you need a permanent storage you may want to store the data in a database.

Sessions work by creating a unique id (UID) for each visitor and store variables based on this UID. The UID is either stored in a cookie or is propagated in the URL.


Starting a PHP Session

Before you can store user information in your PHP session, you must first start up the session.

Note: The session_start() function must appear BEFORE the <html> tag:

<?php session_start(); ?><html>
<body>

</body>
</html>

The code above will register the user’s session with the server, allow you to start saving user information, and assign a UID for that user’s session.


Storing a Session Variable

The correct way to store and retrieve session variables is to use the PHP $_SESSION variable:

<?php
session_start();
// store session data
$_SESSION[‘views’]=1;
?><html>
<body>

<?php
//retrieve session data
echo “Pageviews=”. $_SESSION[‘views’];
?>

</body>
</html>

Output:

Pageviews=1

In the example below, we create a simple page-views counter. The isset() function checks if the “views” variable has already been set. If “views” has been set, we can increment our counter. If “views” doesn’t exist, we create a “views” variable, and set it to 1:

<?php
session_start();if(isset($_SESSION[‘views’]))
$_SESSION[‘views’]=$_SESSION[‘views’]+1;
else
$_SESSION[‘views’]=1;
echo “Views=”. $_SESSION[‘views’];
?>


Destroying a Session

If you wish to delete some session data, you can use the unset() or the session_destroy() function.

The unset() function is used to free the specified session variable:

<?php
session_start();
if(isset($_SESSION[‘views’]))
unset($_SESSION[‘views’]);
?>

You can also completely destroy the session by calling the session_destroy() function:

<?php
session_destroy();
?>

Note: session_destroy() will reset your session and you will lose all your stored session data.

PHP Sending E-mails

PHP allows you to send e-mails directly from a script.


The PHP mail() Function

The PHP mail() function is used to send emails from inside a script.

Syntax

mail(to,subject,message,headers,parameters)
Parameter Description
to Required. Specifies the receiver / receivers of the email
subject Required. Specifies the subject of the email. Note: This parameter cannot contain any newline characters
message Required. Defines the message to be sent. Each line should be separated with a LF (\n). Lines should not exceed 70 characters
headers Optional. Specifies additional headers, like From, Cc, and Bcc. The additional headers should be separated with a CRLF (\r\n)
parameters Optional. Specifies an additional parameter to the sendmail program

Note: For the mail functions to be available, PHP requires an installed and working email system. The program to be used is defined by the configuration settings in the php.ini file. Read more in our PHP Mail reference.


PHP Simple E-Mail

The simplest way to send an email with PHP is to send a text email.

In the example below we first declare the variables ($to, $subject, $message, $from, $headers), then we use the variables in the mail() function to send an e-mail:

<?php
$to = “someone@example.com“;
$subject = “Test mail”;
$message = “Hello! This is a simple email message.”;
$from = “someonelse@example.com“;
$headers = “From:” . $from;
mail($to,$subject,$message,$headers);
echo “Mail Sent.”;
?>

PHP Mail Form

With PHP, you can create a feedback-form on your website. The example below sends a text message to a specified e-mail address:

<html>
<body><?php
if (isset($_REQUEST[’email’]))
//if “email” is filled out, send email
{
//send email
$email = $_REQUEST[’email’] ;
$subject = $_REQUEST[‘subject’] ;
$message = $_REQUEST[‘message’] ;
mail(“someone@example.com“, $subject,
$message, “From:” . $email);
echo “Thank you for using our mail form”;
}
else
//if “email” is not filled out, display the form
{
echo “<form method=’post’ action=’mailform.php’>
Email: <input name=’email’ type=’text’><br>
Subject: <input name=’subject’ type=’text’><br>
Message:<br>
<textarea name=’message’ rows=’15’ cols=’40’>
</textarea><br>
<input type=’submit’>
</form>”;
}
?>

</body>
</html>

This is how the example above works:

  • First, check if the email input field is filled out
  • If it is not set (like when the page is first visited); output the HTML form
  • If it is set (after the form is filled out); send the email from the form
  • When submit is pressed after the form is filled out, the page reloads, sees that the email input is set, and sends the email

Note: This is the simplest way to send e-mail, but it is not secure. In the next chapter of this tutorial you can read more about vulnerabilities in e-mail scripts, and how to validate user input to make it more secure.


PHP Mail Reference

For more information about the PHP mail() function, visit our PHP Mail Reference.

PHP Secure E-mails

There is a weakness in the PHP e-mail script in the previous chapter.


PHP E-mail Injections

First, look at the PHP code from the previous chapter:

<html>
<body><?php
if (isset($_REQUEST[’email’]))
//if “email” is filled out, send email
{
//send email
$email = $_REQUEST[’email’] ;
$subject = $_REQUEST[‘subject’] ;
$message = $_REQUEST[‘message’] ;
mail(“someone@example.com“, “Subject: $subject”,
$message, “From: $email” );
echo “Thank you for using our mail form”;
}
else
//if “email” is not filled out, display the form
{
echo “<form method=’post’ action=’mailform.php’>
Email: <input name=’email’ type=’text’><br>
Subject: <input name=’subject’ type=’text’><br>
Message:<br>
<textarea name=’message’ rows=’15’ cols=’40’>
</textarea><br>
<input type=’submit’>
</form>”;
}
?>

</body>
</html>

The problem with the code above is that unauthorized users can insert data into the mail headers via the input form.

What happens if the user adds the following text to the email input field in the form?

The mail() function puts the text above into the mail headers as usual, and now the header has an extra Cc:, Bcc:, and To: field. When the user clicks the submit button, the e-mail will be sent to all of the addresses above!


PHP Stopping E-mail Injections

The best way to stop e-mail injections is to validate the input.

The code below is the same as in the previous chapter, but now we have added an input validator that checks the email field in the form:

<html>
<body>
<?php
function spamcheck($field)
{
//filter_var() sanitizes the e-mail
//address using FILTER_SANITIZE_EMAIL
$field=filter_var($field, FILTER_SANITIZE_EMAIL);//filter_var() validates the e-mail
//address using FILTER_VALIDATE_EMAIL
if(filter_var($field, FILTER_VALIDATE_EMAIL))
{
return TRUE;
}
else
{
return FALSE;
}
}

if (isset($_REQUEST[’email’]))
{//if “email” is filled out, proceed

//check if the email address is invalid
$mailcheck = spamcheck($_REQUEST[’email’]);
if ($mailcheck==FALSE)
{
echo “Invalid input”;
}
else
{//send email
$email = $_REQUEST[’email’] ;
$subject = $_REQUEST[‘subject’] ;
$message = $_REQUEST[‘message’] ;
mail(“someone@example.com“, “Subject: $subject”,
$message, “From: $email” );
echo “Thank you for using our mail form”;
}
}
else
{//if “email” is not filled out, display the form
echo “<form method=’post’ action=’mailform.php’>
Email: <input name=’email’ type=’text’><br>
Subject: <input name=’subject’ type=’text’><br>
Message:<br>
<textarea name=’message’ rows=’15’ cols=’40’>
</textarea><br>
<input type=’submit’>
</form>”;
}
?>

</body>
</html>

In the code above we use PHP filters to validate input:

  • The FILTER_SANITIZE_EMAIL filter removes all illegal e-mail characters from a string
  • The FILTER_VALIDATE_EMAIL filter validates value as an e-mail address

You can read more about filters in our PHP Filter chapter.

PHP Error Handling

The default error handling in PHP is very simple. An error message with filename, line number and a message describing the error is sent to the browser.


PHP Error Handling

When creating scripts and web applications, error handling is an important part. If your code lacks error checking code, your program may look very unprofessional and you may be open to security risks.

This tutorial contains some of the most common error checking methods in PHP.

We will show different error handling methods:

  • Simple “die()” statements
  • Custom errors and error triggers
  • Error reporting

Basic Error Handling: Using the die() function

The first example shows a simple script that opens a text file:

<?php
$file=fopen(“welcome.txt”,”r”);
?>

If the file does not exist you might get an error like this:

Warning: fopen(welcome.txt) [function.fopen]: failed to open stream:
No such file or directory in C:\webfolder\test.php on line 2

To prevent the user from getting an error message like the one above, we test whether the file exist before we try to access it:

<?php
if(!file_exists(“welcome.txt”))
{
die(“File not found”);
}
else
{
$file=fopen(“welcome.txt”,”r”);
}
?>

Now if the file does not exist you get an error like this:

File not found

The code above is more efficient than the earlier code, because it uses a simple error handling mechanism to stop the script after the error.

However, simply stopping the script is not always the right way to go. Let’s take a look at alternative PHP functions for handling errors.


Creating a Custom Error Handler

Creating a custom error handler is quite simple. We simply create a special function that can be called when an error occurs in PHP.

This function must be able to handle a minimum of two parameters (error level and error message) but can accept up to five parameters (optionally: file, line-number, and the error context):

Syntax

error_function(error_level,error_message,
error_file,error_line,error_context)
Parameter Description
error_level Required. Specifies the error report level for the user-defined error. Must be a value number. See table below for possible error report levels
error_message Required. Specifies the error message for the user-defined error
error_file Optional. Specifies the filename in which the error occurred
error_line Optional. Specifies the line number in which the error occurred
error_context Optional. Specifies an array containing every variable, and their values, in use when the error occurred

Error Report levels

These error report levels are the different types of error the user-defined error handler can be used for:

Value Constant Description
2 E_WARNING Non-fatal run-time errors. Execution of the script is not halted
8 E_NOTICE Run-time notices. The script found something that might be an error, but could also happen when running a script normally
256 E_USER_ERROR Fatal user-generated error. This is like an E_ERROR set by the programmer using the PHP function trigger_error()
512 E_USER_WARNING Non-fatal user-generated warning. This is like an E_WARNING set by the programmer using the PHP function trigger_error()
1024 E_USER_NOTICE User-generated notice. This is like an E_NOTICE set by the programmer using the PHP function trigger_error()
4096 E_RECOVERABLE_ERROR Catchable fatal error. This is like an E_ERROR but can be caught by a user defined handle (see also set_error_handler())
8191 E_ALL All errors and warnings (E_STRICT became a part of E_ALL in PHP 5.4)

Now lets create a function to handle errors:

function customError($errno, $errstr)
{
echo “<b>Error:</b> [$errno] $errstr<br>”;
echo “Ending Script”;
die();
}

The code above is a simple error handling function. When it is triggered, it gets the error level and an error message. It then outputs the error level and message and terminates the script.

Now that we have created an error handling function we need to decide when it should be triggered.


Set Error Handler

The default error handler for PHP is the built in error handler. We are going to make the function above the default error handler for the duration of the script.

It is possible to change the error handler to apply for only some errors, that way the script can handle different errors in different ways. However, in this example we are going to use our custom error handler for all errors:

set_error_handler(“customError”);

Since we want our custom function to handle all errors, the set_error_handler() only needed one parameter, a second parameter could be added to specify an error level.

Example

Testing the error handler by trying to output variable that does not exist:

<?php
//error handler function
function customError($errno, $errstr)
{
echo “<b>Error:</b> [$errno] $errstr”;
}//set error handler
set_error_handler(“customError”);

//trigger error
echo($test);
?>

The output of the code above should be something like this:

Error: [8] Undefined variable: test

Trigger an Error

In a script where users can input data it is useful to trigger errors when an illegal input occurs. In PHP, this is done by the trigger_error() function.

Example

In this example an error occurs if the “test” variable is bigger than “1”:

<?php
$test=2;
if ($test>1)
{
trigger_error(“Value must be 1 or below”);
}
?>

The output of the code above should be something like this:

Notice: Value must be 1 or below
in C:\webfolder\test.php on line 6

An error can be triggered anywhere you wish in a script, and by adding a second parameter, you can specify what error level is triggered.

Possible error types:

  • E_USER_ERROR – Fatal user-generated run-time error. Errors that can not be recovered from. Execution of the script is halted
  • E_USER_WARNING – Non-fatal user-generated run-time warning. Execution of the script is not halted
  • E_USER_NOTICE – Default. User-generated run-time notice. The script found something that might be an error, but could also happen when running a script normally

Example

In this example an E_USER_WARNING occurs if the “test” variable is bigger than “1”. If an E_USER_WARNING occurs we will use our custom error handler and end the script:

<?php
//error handler function
function customError($errno, $errstr)
{
echo “<b>Error:</b> [$errno] $errstr<br>”;
echo “Ending Script”;
die();
}//set error handler
set_error_handler(“customError”,E_USER_WARNING);

//trigger error
$test=2;
if ($test>1)
{
trigger_error(“Value must be 1 or below”,E_USER_WARNING);
}
?>

The output of the code above should be something like this:

Error: [512] Value must be 1 or below
Ending Script

Now that we have learned to create our own errors and how to trigger them, lets take a look at error logging.


Error Logging

By default, PHP sends an error log to the server’s logging system or a file, depending on how the error_log configuration is set in the php.ini file. By using the error_log() function you can send error logs to a specified file or a remote destination.

Sending error messages to yourself by e-mail can be a good way of getting notified of specific errors.

Send an Error Message by E-Mail

In the example below we will send an e-mail with an error message and end the script, if a specific error occurs:

<?php
//error handler function
function customError($errno, $errstr)
{
echo “<b>Error:</b> [$errno] $errstr<br>”;
echo “Webmaster has been notified”;
error_log(“Error: [$errno] $errstr”,1,
someone@example.com“,”From: webmaster@example.com“);
}//set error handler
set_error_handler(“customError”,E_USER_WARNING);

//trigger error
$test=2;
if ($test>1)
{
trigger_error(“Value must be 1 or below”,E_USER_WARNING);
}
?>

The output of the code above should be something like this:

Error: [512] Value must be 1 or below
Webmaster has been notified

And the mail received from the code above looks like this:

Error: [512] Value must be 1 or below

This should not be used with all errors. Regular errors should be logged on the server using the default PHP logging system.

PHP Exception Handling

Exceptions are used to change the normal flow of a script if a specified error occurs.


What is an Exception

With PHP 5 came a new object oriented way of dealing with errors.

Exception handling is used to change the normal flow of the code execution if a specified error (exceptional) condition occurs. This condition is called an exception.

This is what normally happens when an exception is triggered:

  • The current code state is saved
  • The code execution will switch to a predefined (custom) exception handler function
  • Depending on the situation, the handler may then resume the execution from the saved code state, terminate the script execution or continue the script from a different location in the code

We will show different error handling methods:

  • Basic use of Exceptions
  • Creating a custom exception handler
  • Multiple exceptions
  • Re-throwing an exception
  • Setting a top level exception handler

Note: Exceptions should only be used with error conditions, and should not be used to jump to another place in the code at a specified point.


Basic Use of Exceptions

When an exception is thrown, the code following it will not be executed, and PHP will try to find the matching “catch” block.

If an exception is not caught, a fatal error will be issued with an “Uncaught Exception” message.

Lets try to throw an exception without catching it:

<?php
//create function with an exception
function checkNum($number)
{
if($number>1)
{
throw new Exception(“Value must be 1 or below”);
}
return true;
}//trigger exception
checkNum(2);
?>

The code above will get an error like this:

Fatal error: Uncaught exception ‘Exception’
with message ‘Value must be 1 or below’ in C:\webfolder\test.php:6
Stack trace: #0 C:\webfolder\test.php(12):
checkNum(28) #1 {main} thrown in C:\webfolder\test.php on line 6

Try, throw and catch

To avoid the error from the example above, we need to create the proper code to handle an exception.

Proper exception code should include:

  1. Try – A function using an exception should be in a “try” block. If the exception does not trigger, the code will continue as normal. However if the exception triggers, an exception is “thrown”
  2. Throw – This is how you trigger an exception. Each “throw” must have at least one “catch”
  3. Catch – A “catch” block retrieves an exception and creates an object containing the exception information

Lets try to trigger an exception with valid code:

<?php
//create function with an exception
function checkNum($number)
{
if($number>1)
{
throw new Exception(“Value must be 1 or below”);
}
return true;
}//trigger exception in a “try” block
try
{
checkNum(2);
//If the exception is thrown, this text will not be shown
echo ‘If you see this, the number is 1 or below’;
}

//catch exception
catch(Exception $e)
{
echo ‘Message: ‘ .$e->getMessage();
}
?>

The code above will get an error like this:

Message: Value must be 1 or below

Example explained:

The code above throws an exception and catches it:

  1. The checkNum() function is created. It checks if a number is greater than 1. If it is, an exception is thrown
  2. The checkNum() function is called in a “try” block
  3. The exception within the checkNum() function is thrown
  4. The “catch” block retrives the exception and creates an object ($e) containing the exception information
  5. The error message from the exception is echoed by calling $e->getMessage() from the exception object

However, one way to get around the “every throw must have a catch” rule is to set a top level exception handler to handle errors that slip through.


Creating a Custom Exception Class

Creating a custom exception handler is quite simple. We simply create a special class with functions that can be called when an exception occurs in PHP. The class must be an extension of the exception class.

The custom exception class inherits the properties from PHP’s exception class and you can add custom functions to it.

Lets create an exception class:

<?php
class customException extends Exception
{
public function errorMessage()
{
//error message
$errorMsg = ‘Error on line ‘.$this->getLine().’ in ‘.$this->getFile()
.’: <b>’.$this->getMessage().'</b> is not a valid E-Mail address’;
return $errorMsg;
}
}$email = “someone@example…com”;

try
{
//check if
if(filter_var($email, FILTER_VALIDATE_EMAIL) === FALSE)
{
//throw exception if email is not valid
throw new customException($email);
}
}

catch (customException $e)
{
//display custom message
echo $e->errorMessage();
}
?>

The new class is a copy of the old exception class with an addition of the errorMessage() function. Since it is a copy of the old class, and it inherits the properties and methods from the old class, we can use the exception class methods like getLine() and getFile() and getMessage().

Example explained:

The code above throws an exception and catches it with a custom exception class:

  1. The customException() class is created as an extension of the old exception class. This way it inherits all methods and properties from the old exception class
  2. The errorMessage() function is created. This function returns an error message if an e-mail address is invalid
  3. The $email variable is set to a string that is not a valid e-mail address
  4. The “try” block is executed and an exception is thrown since the e-mail address is invalid
  5. The “catch” block catches the exception and displays the error message

Multiple Exceptions

It is possible for a script to use multiple exceptions to check for multiple conditions.

It is possible to use several if..else blocks, a switch, or nest multiple exceptions. These exceptions can use different exception classes and return different error messages:

<?php
class customException extends Exception
{
public function errorMessage()
{
//error message
$errorMsg = ‘Error on line ‘.$this->getLine().’ in ‘.$this->getFile()
.’: <b>’.$this->getMessage().'</b> is not a valid E-Mail address’;
return $errorMsg;
}
}$email = “someone@example.com“;

try
{
//check if
if(filter_var($email, FILTER_VALIDATE_EMAIL) === FALSE)
{
//throw exception if email is not valid
throw new customException($email);
}
//check for “example” in mail address
if(strpos($email, “example”) !== FALSE)
{
throw new Exception(“$email is an example e-mail”);
}
}

catch (customException $e)
{
echo $e->errorMessage();
}

catch(Exception $e)
{
echo $e->getMessage();
}
?>

Example explained:

The code above tests two conditions and throws an exception if any of the conditions are not met:

  1. The customException() class is created as an extension of the old exception class. This way it inherits all methods and properties from the old exception class
  2. The errorMessage() function is created. This function returns an error message if an e-mail address is invalid
  3. The $email variable is set to a string that is a valid e-mail address, but contains the string “example”
  4. The “try” block is executed and an exception is not thrown on the first condition
  5. The second condition triggers an exception since the e-mail contains the string “example”
  6. The “catch” block catches the exception and displays the correct error message

If the exception thrown were of the class customException and there were no customException catch, only the base exception catch, the exception would be handled there.


Re-throwing Exceptions

Sometimes, when an exception is thrown, you may wish to handle it differently than the standard way. It is possible to throw an exception a second time within a “catch” block.

A script should hide system errors from users. System errors may be important for the coder, but is of no interest to the user. To make things easier for the user you can re-throw the exception with a user friendly message:

<?php
class customException extends Exception
{
public function errorMessage()
{
//error message
$errorMsg = $this->getMessage().’ is not a valid E-Mail address.’;
return $errorMsg;
}
}$email = “someone@example.com“;

try
{
try
{
//check for “example” in mail address
if(strpos($email, “example”) !== FALSE)
{
//throw exception if email is not valid
throw new Exception($email);
}
}
catch(Exception $e)
{
//re-throw exception
throw new customException($email);
}
}

catch (customException $e)
{
//display custom message
echo $e->errorMessage();
}
?>

Example explained:

The code above tests if the email-address contains the string “example” in it, if it does, the exception is re-thrown:

  1. The customException() class is created as an extension of the old exception class. This way it inherits all methods and properties from the old exception class
  2. The errorMessage() function is created. This function returns an error message if an e-mail address is invalid
  3. The $email variable is set to a string that is a valid e-mail address, but contains the string “example”
  4. The “try” block contains another “try” block to make it possible to re-throw the exception
  5. The exception is triggered since the e-mail contains the string “example”
  6. The “catch” block catches the exception and re-throws a “customException”
  7. The “customException” is caught and displays an error message

If the exception is not caught in its current “try” block, it will search for a catch block on “higher levels”.


Set a Top Level Exception Handler

The set_exception_handler() function sets a user-defined function to handle all uncaught exceptions.

<?php
function myException($exception)
{
echo “<b>Exception:</b> ” , $exception->getMessage();
}set_exception_handler(‘myException’);

throw new Exception(‘Uncaught Exception occurred’);
?>

The output of the code above should be something like this:

Exception: Uncaught Exception occurred

In the code above there was no “catch” block. Instead, the top level exception handler triggered. This function should be used to catch uncaught exceptions.


Rules for exceptions

  • Code may be surrounded in a try block, to help catch potential exceptions
  • Each try block or “throw” must have at least one corresponding catch block
  • Multiple catch blocks can be used to catch different classes of exceptions
  • Exceptions can be thrown (or re-thrown) in a catch block within a try block

A simple rule: If you throw something, you have to catch it.

PHP Filter

PHP filters are used to validate and filter data coming from insecure sources, like user input.


What is a PHP Filter?

A PHP filter is used to validate and filter data coming from insecure sources.

To test, validate and filter user input or custom data is an important part of any web application.

The PHP filter extension is designed to make data filtering easier and quicker.


Why use a Filter?

Almost all web applications depend on external input. Usually this comes from a user or another application (like a web service). By using filters you can be sure your application gets the correct input type.

You should always filter all external data!

Input filtering is one of the most important application security issues.

What is external data?

  • Input data from a form
  • Cookies
  • Web services data
  • Server variables
  • Database query results

Functions and Filters

To filter a variable, use one of the following filter functions:

  • filter_var() – Filters a single variable with a specified filter
  • filter_var_array() – Filter several variables with the same or different filters
  • filter_input – Get one input variable and filter it
  • filter_input_array – Get several input variables and filter them with the same or different filters

In the example below, we validate an integer using the filter_var() function:

<?php
$int = 123;if(!filter_var($int, FILTER_VALIDATE_INT))
{
echo(“Integer is not valid”);
}
else
{
echo(“Integer is valid”);
}
?>

The code above uses the “FILTER_VALIDATE_INT”  filter to filter the variable. Since the integer is valid, the output of the code above will be: “Integer is valid”.

If we try with a variable that is not an integer (like “123abc”), the output will be: “Integer is not valid”.

For a complete list of functions and filters, visit our PHP Filter Reference.


Validating and Sanitizing

There are two kinds of filters:

Validating filters:

  • Are used to validate user input
  • Strict format rules (like URL or E-Mail validating)
  • Returns the expected type on success or FALSE on failure

Sanitizing filters:

  • Are used to allow or disallow specified characters in a string
  • No data format rules
  • Always return the string

Options and Flags

Options and flags are used to add additional filtering options to the specified filters.

Different filters have different options and flags.

In the example below, we validate an integer using the filter_var() and the “min_range” and “max_range” options:

<?php
$var=300;$int_options = array(
“options”=>array
(
“min_range”=>0,
“max_range”=>256
)
);

if(!filter_var($var, FILTER_VALIDATE_INT, $int_options))
{
echo(“Integer is not valid”);
}
else
{
echo(“Integer is valid”);
}
?>

Like the code above, options must be put in an associative array with the name “options”. If a flag is used it does not need to be in an array.

Since the integer is “300” it is not in the specified range, and the output of the code above will be: “Integer is not valid”.

For a complete list of functions and filters, visit our PHP Filter Reference. Check each filter to see what options and flags are available.


Validate Input

Let’s try validating input from a form.

The first thing we need to do is to confirm that the input data we are looking for exists.

Then we filter the input data using the filter_input() function.

In the example below, the input variable “email” is sent to the PHP page:

<?php
if(!filter_has_var(INPUT_GET, “email”))
{
echo(“Input type does not exist”);
}
else
{
if (!filter_input(INPUT_GET, “email”, FILTER_VALIDATE_EMAIL))
{
echo “E-Mail is not valid”;
}
else
{
echo “E-Mail is valid”;
}
}
?>

Example Explained

The example above has an input (email) sent to it using the “GET” method:

  1. Check if an “email” input variable of the “GET” type exist
  2. If the input variable exists, check if it is a valid e-mail address

Sanitize Input

Let’s try cleaning up an URL sent from a form.

First we confirm that the input data we are looking for exists.

Then we sanitize the input data using the filter_input() function.

In the example below, the input variable “url” is sent to the PHP page:

<?php
if(!filter_has_var(INPUT_POST, “url”))
{
echo(“Input type does not exist”);
}
else
{
$url = filter_input(INPUT_POST,
“url”, FILTER_SANITIZE_URL);
}
?>

Example Explained

The example above has an input (url) sent to it using the “POST” method:

  1. Check if the “url” input of the “POST” type exists
  2. If the input variable exists, sanitize (take away invalid characters) and store it in the $url variable

If the input variable is a string like this “http://www.W3ååSchøøools.com/“, the $url variable after the sanitizing will look like this:


Filter Multiple Inputs

A form almost always consist of more than one input field. To avoid calling the filter_var or filter_input functions over and over, we can use the filter_var_array or the filter_input_array functions.

In this example we use the filter_input_array() function to filter three GET variables. The received GET variables is a name, an age and an e-mail address:

<?php
$filters = array
(
“name” => array
(
“filter”=>FILTER_SANITIZE_STRING
),
“age” => array
(
“filter”=>FILTER_VALIDATE_INT,
“options”=>array
(
“min_range”=>1,
“max_range”=>120
)
),
“email”=> FILTER_VALIDATE_EMAIL
);$result = filter_input_array(INPUT_GET, $filters);

if (!$result[“age”])
{
echo(“Age must be a number between 1 and 120.<br>”);
}
elseif(!$result[“email”])
{
echo(“E-Mail is not valid.<br>”);
}
else
{
echo(“User input is valid”);
}
?>

Example Explained

The example above has three inputs (name, age and email) sent to it using the “GET” method:

  1. Set an array containing the name of input variables and the filters used on the specified input variables
  2. Call the filter_input_array() function with the GET input variables and the array we just set
  3. Check the “age” and “email” variables in the $result variable for invalid inputs. (If any of the input variables are invalid, that input variable will be FALSE after the filter_input_array() function)

The second parameter of the filter_input_array() function can be an array or a single filter ID.

If the parameter is a single filter ID all values in the input array are filtered by the specified filter.

If the parameter is an array it must follow these rules:

  • Must be an associative array containing an input variable as an array key (like the “age” input variable)
  • The array value must be a filter ID or an array specifying the filter, flags and options

Using Filter Callback

It is possible to call a user defined function and use it as a filter using the FILTER_CALLBACK filter. This way, we have full control of the data filtering.

You can create your own user defined function or use an existing PHP function

The function you wish to use to filter is specified the same way as an option is specified. In an associative array with the name “options”

In the example below, we use a user created function to convert all  “_” to whitespaces:

<?php
function convertSpace($string)
{
return str_replace(“_”, ” “, $string);
}$string = “Peter_is_a_great_guy!”;

echo filter_var($string, FILTER_CALLBACK,
array(“options”=>”convertSpace”));
?>

The result from the code above should look like this:

Peter is a great guy!

Example Explained

The example above converts all “_” to whitespaces:

  1. Create a function to replace “_” to whitespaces
  2. Call the filter_var() function with the FILTER_CALLBACK filter and an array containing our function
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7 thoughts on “Learning PHP(credit to w3 School) – PHP Advance Collection-1

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  4. Is it worth using meta description on blog posts then?
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    Are you active on any forums?

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