What is the function of mysql_insert_id in PHP and how does it handle multiple asynchronous requests?

The mysql_insert_id function in PHP returns the ID generated by a query on a table with an AUTO_INCREMENT column. To handle multiple asynchronous requests, you can store the last inserted ID in a session variable and retrieve it when needed.

// Store the last inserted ID in a session variable
$_SESSION['last_insert_id'] = mysql_insert_id();

// Retrieve the last inserted ID from the session variable
$last_insert_id = $_SESSION['last_insert_id'];