? Filters in PHP (Validation + Sanitization)

PHP filters are used to validate and sanitize input data — especially helpful when dealing with form data, URLs, cookies, or any external input.

? What Are Filters?

Filters are functions from the filter extension that ensure input is:

• ? Valid — matches a specific format (e.g., email, integer)

• ? Sanitized — cleaned from illegal or harmful characters

? 1. Sanitization Filters

These remove or encode unwanted characters.

$name = "<b>John</b>";$clean_name = filter_var($name, FILTER_SANITIZE_STRING); // Deprecated$clean_name = strip_tags($name); // Preferred nowecho $clean_name; // Output: John

Common Sanitization Filters:

? 2. Validation Filters

These check if the input is valid (returns the value on success or false on failure).

$email = "user@example.com";if (filter_var($email, FILTER_VALIDATE_EMAIL)) {    echo "Valid email!";} else {    echo "Invalid email!";}

Common Validation Filters:

? 3. Validate with Options

$age = 25;$options = ["options" => ["min_range" => 18, "max_range" => 99]];if (filter_var($age, FILTER_VALIDATE_INT, $options)) {    echo "Valid age.";} else {    echo "Age out of range.";}

? 4. Using filter_input()

Safely get and filter input from external sources like GET, POST, COOKIE.

$email = filter_input(INPUT_POST, "email", FILTER_VALIDATE_EMAIL);if ($email) {    echo "Email is valid!";} else {    echo "Invalid email.";}

? Best Practices

• Always sanitize before displaying user input.

• Always validate before storing input.

• Combine both for maximum safety.