How can PHP developers effectively validate and sanitize user input from forms?

To effectively validate and sanitize user input from forms in PHP, developers can use functions like filter_var() to validate input against a specific filter, such as FILTER_VALIDATE_EMAIL for email validation. They can also use functions like htmlspecialchars() to sanitize input and prevent XSS attacks by converting special characters to HTML entities. Additionally, developers should always validate input on the server-side to ensure data integrity and security.

// Validate and sanitize user input from a form
$email = $_POST['email'];

// Validate email input
if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
    echo "Invalid email format";
}

// Sanitize input to prevent XSS attacks
$sanitized_email = htmlspecialchars($email);

// Use $sanitized_email for further processing