When AJAX sends data to the server, PHP receives it using superglobal variables.
PHP uses different variables based on request method.
Data sent using GET method is accessed through the $_GET variable.
Data sent using POST method is accessed through the $_POST variable.
PHP can check whether data is received before using it.
Using validation helps prevent errors and undefined variable issues.
PHP processes the received data and prepares a response for AJAX.
After completing this lesson, you understand how PHP receives and processes AJAX data.