What are the best practices for handling form validation and error handling in PHP applications?

When handling form validation and error handling in PHP applications, it is important to validate user input to ensure data integrity and security. This can be achieved by using built-in PHP functions like filter_var() or regular expressions to validate input fields. Additionally, error handling should be implemented to gracefully handle any errors that may occur during form submission, such as displaying error messages to the user.

// Example of form validation and error handling in PHP

// Validate form input
$name = $_POST['name'];
$email = $_POST['email'];

if(empty($name) || empty($email)) {
    echo "Please fill out all required fields.";
    exit;
}

if(!filter_var($email, FILTER_VALIDATE_EMAIL)) {
    echo "Invalid email format.";
    exit;
}

// Process form submission
// Your code to handle form submission goes here