When using Ajax with PHP, which of the following are necessary to verify success?

Which of the following answers are correct ?

• HTTP ready state of TRUE
• HTTP ready state of 4
• HTTP status code <开发者_运维问答 400
• HTTP status of 200
• Data present in the response

both HTTP status of 200 and HTTP ready state of TRUE

In all my apps, I require only ready state 4 for success, which means as little as: the request is done and the response (if any) is available.

But like Madmartigan very wisely commented: define your version of success.

Usually, an HTTP ready state of 4 and HTTP status code of 200 is needed in order to guarantee that data has been successfully transferred back to your program.