从MySQL数据库获取自动递增的值

I am writing a PHP script where data is inserted into a table using a query like "INSERT INTO y (x, x, x) VALUES (z, z, z). I have a unique, primary, auto-incrementing key that is in the table. How can I fetch that number right after the data is inserted and the key is updated with the new row?I am writing a PHP script where data is inserte