How can the use of special characters in form input impact the processing of PHP scripts?

Special characters in form input can impact the processing of PHP scripts by potentially causing security vulnerabilities such as SQL injection or cross-site scripting attacks. To mitigate this risk, it is important to properly sanitize and validate user input before using it in your PHP scripts. One way to do this is by using functions like htmlspecialchars() or mysqli_real_escape_string() to escape special characters and prevent them from being interpreted as code.

// Example of sanitizing user input using htmlspecialchars()
$user_input = $_POST['user_input'];
$clean_input = htmlspecialchars($user_input);
// Now $clean_input can be safely used in your PHP script