PHP Filters

PHP filter_var() Function

The filter_var() function validates and sanitises data.

The filter_var() function applies a filter on a single variable. It requires the two pieces of information:

• The variable to check.
• The type of check we want use

The following is the syntax for this function:

filter_var(variable, filter)

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Validating an Integer

The filter_var() function is used in the following example to determine whether the variable $int is an integer. If $int is an integer, the following code will return "Valid Integer." The output will be "Not Valid Integer" if $int is not an integer.

Example:

<?php
$int = 50;

if (!filter_var($int, FILTER_VALIDATE_INT) === false) {
 echo("Valid Integer");
} else {
 echo("Not Valid Integer");
}
?>

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Output:

Sanitizing a String

The filter_var() function is used in the following example to remove all HTML tags from a string:

Example:

<?php
// Sample user comment
$string = "<h1>Hello Worlds! I am removing HTML tags.</h1>";

// Sanitise and print comment string
$sanitisedstring = filter_var($string, FILTER_SANITIZE_STRING);
echo $sanitisedstring;
?>

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The output of the code will be a string without all these HTML tags.

Output:

Validating an IP Address

The filter_var() function is used in the following example to determine whether a variable is a legitimate IP address:

Example:

<?php
$ipAddress = "99920.0.0.1";

if (!filter_var($ipAddress, FILTER_VALIDATE_IP) === false) {
 echo("$ipAddress is a valid IP address");
} else {
 echo("$ipAddress is not a valid IP address");
}
?>

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Output:

Sanitising and Validating an Email Address

The filter_var() function is used in the following example to remove all prohibited characters from the variable and then determines whether it is a valid email address:

Example:

<?php
$email = "@example.test@example.com";

// Remove all illegal characters from email
$email = filter_var($email, FILTER_SANITIZE_EMAIL);

// Validate email
if (!filter_var($email, FILTER_VALIDATE_EMAIL) === false) {
 echo("It is a valid email address");
} else {
 echo("It is not a valid email address");
}
?>

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Output:

Sanitizing and Validating a URL

The filter_var() function is used in the following example to eliminate all prohibited characters from a URL before checking if $url is a valid URL:

Example:

<?php
$url = "https:/www.codingninjas.com";

// Remove all illegal characters from a URL

$url = filter_var($url, FILTER_SANITIZE_URL);

// Validate url

if (!filter_var($url, FILTER_VALIDATE_URL) === false) {
 echo("Valid URL");
} else {
 echo("Not a valid URL");
}
?>

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Output:

PHP Filter Functions

PHP has several filter functions to filter the data coming from various sources.

PHP Predefined Filter Constants

PHP has many predefined filter constants. Some of them are listed below.

Validate filter constants

These PHP filter constants are used to validate data.

Sanitise filter constants

These PHP filter constants are used to filter the data for any invalid characters.

FAQs

1. What are filters in PHP?
   External input is validated and sanitized using PHP filter extensions. The PHP filter extension includes many of the functions required for validating user input; it is designed to make data validation easier and faster.
    
2. How many types of filters are present in PHP?
   There are two main types of filters in PHP: validation and sanitization.
   Validation is a process done to ensure that the data is in the right format.
   Sanitization is the process of removing any illegal characters from data. However, it does not validate the data.
    
3. What does data sanitization mean in PHP?
   Data sanitization refers to the removal of any unlawful characters from the data. One of the most important tasks in a web application is sanitizing user input. PHP includes a native filter extension that you can use to sanitize the data to make this work easier.

Key Takeaways

Any website is subjected to various inputs from a variety of sources, making it critical for us to safeguard our website against potential threats. External data can be validated and sanitized using PHP filters extensions. Many predefined PHP filters constants exist, all of which are designed to make data validation easier and faster.

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