What are the potential pitfalls of using regular expressions to validate user input in PHP?

Using regular expressions to validate user input in PHP can lead to complex and hard-to-maintain code. It can also potentially introduce security vulnerabilities if not properly sanitized. To mitigate these pitfalls, consider using PHP's built-in filter_var function with appropriate filter flags for validation. 

// Using filter_var for input validation
$input = $_POST['input'];

if (filter_var($input, FILTER_VALIDATE_EMAIL)) {
    // Proceed with valid email input
} else {
    // Handle invalid input
}

Keywords

regular expressions user input validation PHP pitfalls

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