What best practices should PHP developers follow when designing and implementing form processing and algorithmic calculations in PHP?

When designing and implementing form processing and algorithmic calculations in PHP, PHP developers should follow best practices such as validating user input, sanitizing data to prevent SQL injection attacks, and using secure encryption methods for sensitive information. Additionally, developers should optimize their code for performance by avoiding unnecessary loops and database queries.

// Example of validating user input in PHP form processing
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    $name = $_POST["name"];
    $email = $_POST["email"];

    // Validate name
    if (empty($name)) {
        $errors[] = "Name is required";
    }

    // Validate email
    if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
        $errors[] = "Invalid email format";
    }

    // Process form if no errors
    if (empty($errors)) {
        // Process form data
    }
}