PHP | filter_var() Function

Last Updated : 18 Nov, 2019
The filter_var() function filters a variable with the specified filter. This function is used to both validate and sanitize the data. Syntax :- 
filter_var(var, filtername, options)
Parameters: This function accepts three parameters and are described below:
  1. var : It is the required field. It denotes the variable to filter.
  2. filtername : It is used to specify the ID or name of the filter to use. Default is FILTER_DEFAULT, which results in no filtering. It is optional field.
  3. options : It is used to specify one or more flags/options to use. Check each filter for possible options and flags. It is also optional field.
Return Value: It returns the filtered data on success, or FALSE on failure. Below are some different applications of filter_var() function:
  • Sanitize a string : In the below example we sanitize a string Example:- PHP 
    <?php

$str = "<h1>GeeksforGeeks!</h1>";
$newstr = filter_var($str, FILTER_SANITIZE_STRING);
echo $newstr;

?>
    Output :- 
    GeeksforGeeks!
  • Validate an Integer : The below example uses the filter_var() function to check if the variable $int is an integer. If $int is an integer, the output of the code below will be: "Integer is valid". If $int is not an integer, the output will be: "Integer is not valid": Example:- PHP 
    <?php

$int = 200;

if (filter_var($int, FILTER_VALIDATE_INT) === 0 || 
    !filter_var($int, FILTER_VALIDATE_INT) === false) 
{
    echo("Integer is valid");
} 
else 
{
    echo("Integer is not valid");
}

?>
    Output :- 
    Integer is valid
  • Validate an IP Address : The following example uses the filter_var() function to check if the variable $ip is a valid IP address: Example :- PHP 
    <?php

$ip = "129.0.0.1";

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

?>
    Output :- 
    129.0.0.1 is a valid IP address
  • Sanitize and Validate an Email Address : The following example uses the filter_var() function to first remove all illegal characters from the $email variable, then check if it is a valid email address: Example :- PHP 
    <?php

$email = "[email protected]";

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

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

?>
    Output :- 
    [email protected] is a valid email address
  • Sanitize and Validate a URL : The following example uses the filter_var() function to first remove all illegal characters from a URL, then check if $url is a valid URL: Example :- PHP 
    <?php

$url = "https://www.geeksforgeeks.org/";

// Remove all illegal characters from a url
$url = filter_var($url, FILTER_SANITIZE_URL);

// Validate url
if (!filter_var($url, FILTER_VALIDATE_URL) === false) {
    echo("$url is a valid URL");
} else {
    echo("$url is not a valid URL");
}

?>
    Output :- 
    https://www.geeksforgeeks.org/ is a valid URL
Reference: https://www.php.net/manual/en/function.filter-var.php
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