What security considerations should be taken into account when handling user input in PHP forms?

When handling user input in PHP forms, it is crucial to sanitize and validate the input to prevent security vulnerabilities such as SQL injection, cross-site scripting (XSS), and other forms of attacks. Sanitizing input involves removing any potentially harmful characters or code from the input, while validation ensures that the input meets the expected format and criteria. 

// Sanitize user input
$input = filter_var($_POST['input_field'], FILTER_SANITIZE_STRING);

// Validate user input
if (preg_match("/^[a-zA-Z0-9]+$/", $input)) {
    // Input is valid, proceed with processing
} else {
    // Input is invalid, display error message
    echo "Invalid input. Please enter alphanumeric characters only.";
}

Keywords

SQL injection Cross-site scripting (XSS) Input validation Sanitization Escaping

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