PHP filter_var_array: How to Validate Multiple Inputs

The filter_var_array() appeared to make input validation simple and sanitization in PHP.

It handles multiple inputs with different filters was repetitive and error-prone.

Here is what we cover in this article:

• What filter_var_array is in PHP and how it works.
• How to validate form data with it.
• Validate email and URLs. Also, validate numbers with the filter_var_array function.

Let’s move on to its definition and how it works.

Understand the PHP filter_var_array

The filter_var_array() is a PHP function that filters multiple values in an array using specified validation and sanitization rules. It applies different filters to each element.

The syntax:

filter_var_array($array, $options, $add_empty)

Here are the parameters:

• $array refers to the input array to filter. It should array type.
• $options parameter is an array of filters (key-value pairs) or a single filter for all values.
• $add_empty is an optional ( default true). It controls whether missing keys should be added as null.

It returns:

• The filtered array on success.
• A false value if filtering fails.
• Returns null if the input is not an array.

Example 1: Validate Form Data with filter_var_array in PHP

Here is an example to validate form data:

$data = [
    'name' => 'FlatCoding Username',
    'email' => 'flatcodinguser@example.com',
    'age' => '25'
];

// It defines validation rules
$filters = [
    'name'  => FILTER_SANITIZE_STRING,
    'email' => FILTER_VALIDATE_EMAIL,
    'age'   => [
        'filter'  => FILTER_VALIDATE_INT,
        'options' => ['min_range' => 18, 'max_range' => 100]
    ]
];

// Apply filters
$validatedData = filter_var_array($data, $filters);

// Check if validation passed
if ($validatedData['email'] === false || $validatedData['age'] === false) {
    echo "Invalid input detected.";
} else {
    print_r($validatedData);
}

Output:

Array
(
    [name] => FlatCoding Username
    [email] => flatcodinguser@example.com
    [age] => 25
)

How does it work?

• FILTER_SANITIZE_STRING removes unwanted characters from name.
• FILTER_VALIDATE_EMAIL ensures email is valid.
• FILTER_VALIDATE_INT checks if age is a number between 18 and 100.

This method ensures safe and validated user input.

Example 2: Validate Email, URLs, and Numbers with filter_var_array in PHP

This example shows you how to validate emails, URLs, and numbers:

// Sample input data (usually from $_POST or $_GET)
$data = [
    'email'   => 'user@example.com',
    'website' => 'https://flatcoding.com',
    'age'     => '30',
    'price'   => '19.99'
];

// Define validation rules
$filters = [
    'email'   => FILTER_VALIDATE_EMAIL,
    'website' => FILTER_VALIDATE_URL,
    'age'     => FILTER_VALIDATE_INT,
    'price'   => FILTER_VALIDATE_FLOAT
];

// Apply filters
$validatedData = filter_var_array($data, $filters);

// Check for validation errors
if (in_array(false, $validatedData, true)) {
    echo "Invalid input detected.";
} else {
    print_r($validatedData);
}

Output:

Array
(
    [email] => user@example.com
    [website] => https://flatcoding.com
    [age] => 30
    [price] => 19.99
)

Here is how it works:

• FILTER_VALIDATE_EMAIL help you to make sure the email is valid.
• FILTER_VALIDATE_URL checks if the URL format is correct.
• FILTER_VALIDATE_INT makes sure age is a valid integer.
• FILTER_VALIDATE_FLOAT checkes price is a valid decimal number.

This method validates multiple input types at once.

Example 3: Customize Filter with filter_var_array for Advanced Validation

You can customize filter_var_array() using advanced validation options like range limits, required formats, and flags.

// Sample input data (usually from $_POST or $_GET)
$data = [
    'username' => 'JohnDoe123',
    'email'    => 'user@example.com',
    'age'      => '25',
    'website'  => 'https://example.com',
    'ip'       => '192.168.1.1'
];

// Define custom filters
$filters = [
    'username' => [
        'filter'  => FILTER_CALLBACK,
        'options' => function ($value) {
            return preg_match('/^[a-zA-Z0-9_]{5,20}$/', $value) ? $value : false;
        }
    ],
    'email'   => FILTER_VALIDATE_EMAIL,
    'age'     => [
        'filter'  => FILTER_VALIDATE_INT,
        'options' => ['min_range' => 18, 'max_range' => 65]
    ],
    'website' => [
        'filter'  => FILTER_VALIDATE_URL,
        'flags'   => FILTER_FLAG_PATH_REQUIRED
    ],
    'ip'      => FILTER_VALIDATE_IP
];

// Apply filters
$validatedData = filter_var_array($data, $filters);

// Check for validation errors
if (in_array(false, $validatedData, true)) {
    echo "Invalid input detected.";
} else {
    print_r($validatedData);
}

Output:

Invalid input detected.

Here is how it works:

• I used FILTER_CALLBACK with a regex pattern. Only allows letters, numbers, and underscores (5-20 characters).
• In the age we make sure the age is between 18 and 65.
• It also requires a valid URL with a path (FILTER_FLAG_PATH_REQUIRED).
• We also check for a valid IP format.

This method provides stricter validation and more control over input processing.

Wrapping Up

You learned in this article how filter_var_array() to make input validation simple and sanitization in PHP. You also saw practical examples of validating form data and emails.

Also, you learned how to validate URLs and numbers with advanced filtering options.

Here is a quick recap:

• filter_var_array() processes multiple inputs at once using different filters.
• You can sanitize and validate form data to prevent invalid input.
• It supports email, URL, integer, and float validation.
• Advanced filtering allows custom validation with FILTER_CALLBACK, range checks, and flags.

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