PHP filter_has_var Function

Summary: in this tutorial, you’ll learn about the filter_has_var() function and how to use it to check if a variable exists in an input.

Introduction to the filter_has_var() function #

The filter_has_var() function checks if a variable of a specific input type exists. The filter_has_var() function is a part of PHP’s filter extension.

Here’s the syntax of the filter_has_var() function:

filter_has_var ( int $input_type , string $var_name ) : boolCode language: PHP (php)

The function has the two parameters:

• $input_type is the type of input that you want to check for a variable. The valid input types are INPUT_GET, INPUT_POST, INPUT_COOKIE, INPUT_SERVER, or INPUT_ENV.
• $var_name is the name of the variable to check.

The filter_has_var() function returns true if the $var_name exists in the $input_type or false otherwise.

The filter_has_var() function only checks if a variable exists. It does not validate or sanitize the input. Typically, you’ll use the filter_has_var() function with other functions like filter_input() or filter_var() to deal with security.

Checking a GET variable #

The following example uses the filter_has_var() function to check if the term exists in the INPUT_GET:

<?php

if (filter_has_var(INPUT_GET, 'term')) {
    echo "Term is set in GET: " . $_GET['name'];
} else {
    echo "Term is not set.";
}
Code language: HTML, XML (xml)

Checking a POST variable #

The following example shows how to use the filter_has_var() function to check if the email exists in INPUT_POST:

<?php

if (filter_has_var(INPUT_POST, 'email')) {
    echo "Email is set: " . $_POST['email'];
} else {
    echo "Email is not set.";
}
Code language: HTML, XML (xml)

filter_has_var vs. isset #

The isset() function returns true if a variable is declared and not null. For example, the following checks if the name variable in the $_POST array:

<?php

if(isset($_POST['name'])) {
    // process the name
}Code language: PHP (php)

In this example, the isset() checks if the $_POST variable has a key 'name' and the $_POST['name'] is not null.

However, the isset() doesn’t check whether the name variable comes from the HTTP request or not. For example:

<?php

$_POST['email'] = '[email protected]';

if(isset($_POST['email'])) { // return true
    // ...
}Code language: PHP (php)

In this example:

• First, manually set the $_POST['email'] to a value.
• Then, use the isset() function to check if the email variable exists.

As a result, the isset() function returns true.

Unlike the isset() function, the filter_has_var() function doesn’t read the contents of the $_POST array. It checks the variables in the request’s body. Therefore, the following example returns false:

<?php

$_POST['email'] = '[email protected]';

if(filter_has_var(INPUT_POST, 'email')) { // return false
    // ...
}Code language: PHP (php)

Summary #

• Use the filter_has_var() function to check if a variable exists in a specified type, including INPUT_POST, INPUT_GET, INPUT_COOKIE, INPUT_SERVER, or INPUT_ENV.