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 specified type exists. Here’s the syntax of the filter_has_var() function:

filter_has_var ( int $input_type , string $var_name ) : boolCode language: Python (python)

The filter_has_var() function has the following parameter:

$input_type is the type of input that you want to search 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 PHP filter_has_var() function example

We’ll create a very simple form to demonstrate the filter_has_var() function.

First, create the following files and directories:

.
├── css
│   └── style.css
├── inc
│   ├── get.php
│   ├── post.php
│   └── .htaccess
└── index.phpCode language: Python (python)

Second, add the following code to the index.php file:

<?php

if ($_SERVER['REQUEST_METHOD'] === 'GET') {
	require 'inc/get.php';
} else {
	require 'inc/post.php';
}Code language: Python (python)

If the request is GET, the index.php file loads the form from the get.php file. Otherwise, it loads the code for processing the form in the post.php file.

Third, create a form in the get.php file:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <link rel="stylesheet" href="css/style.css">
    <title>PHP filter_has_var Demo</title>
</head>
<body>
    <div class="container">
        <form action="<?php echo htmlspecialchars($_SERVER['PHP_SELF']) ?>" method="post" class="shaddow">
            <label for="name">Name:</label>
            <input type="text" name="name" id="name">
            <input type="submit" value="Submit">
        </form>
    </div>
</body>
</html>Code language: HTML, XML (xml)

Finally, in the post.php file, use the filter_has_var() function to check if the form data contains the $name variable:

<?php

// check the name variable in the post request
if (filter_has_var(INPUT_POST, 'name')) {
	echo 'The name variable exists:' . htmlspecialchars($_POST['name']);
} else {
	echo 'The name is required!';
}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: Python (python)

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 if 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: Python (python)

In this example, we first manually set the $_POST['email'] to a value. And then we 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: Python (python)

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.

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