What are the best practices for handling user input from forms in PHP to prevent security vulnerabilities or unexpected behavior?

To prevent security vulnerabilities or unexpected behavior when handling user input from forms in PHP, it is crucial to sanitize and validate the input data before using it in your application. This can help prevent SQL injection, cross-site scripting (XSS) attacks, and other security risks. One way to achieve this is by using PHP's filter_var() function to sanitize and validate the input data. 

// Sanitize and validate user input from a form field
$userInput = $_POST['user_input'] ?? ''; // Get the user input from the form field

// Sanitize the input data
$sanitizedInput = filter_var($userInput, FILTER_SANITIZE_STRING);

// Validate the input data
if (filter_var($sanitizedInput, FILTER_VALIDATE_STRING)) {
    // Proceed with using the sanitized and validated input data
    echo "Input is valid: " . $sanitizedInput;
} else {
    // Handle invalid input
    echo "Invalid input detected";
}

Keywords

SQL injection cross-site scripting input validation htmlspecialchars prepared statements

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