Are there any best practices for validating user input in PHP forms?

When validating user input in PHP forms, it is important to use server-side validation to ensure data integrity and security. Some best practices include checking for required fields, validating data types, sanitizing input to prevent SQL injection and cross-site scripting attacks, and displaying clear error messages to users. 

// Example of validating user input in a PHP form
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    // Check if required fields are not empty
    if (empty($_POST["username"]) || empty($_POST["password"])) {
        $error = "Username and password are required";
    } else {
        // Validate data types
        $username = filter_var($_POST["username"], FILTER_SANITIZE_STRING);
        $password = filter_var($_POST["password"], FILTER_SANITIZE_STRING);

        // Sanitize input to prevent SQL injection
        $username = mysqli_real_escape_string($conn, $username);
        $password = mysqli_real_escape_string($conn, $password);

        // Perform further validation or processing
        // ...
    }
}

Keywords

Sanitize validation filter_var htmlspecialchars preg_match

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