xmlhttprequest标头定义的含义

Question

I should write a journal when I do changes in my code to make it work, sometimes, in a rush, I just put it to work without knowing exactly why.

I did change a setRequestHeader of a xmlhttprequest from "application/x-www-form-urlencoded; charset=UTF-8" to "application/octet-stream", for some reason, but later, when trying to reuse the code to send some vars by POST to a php, it didn't work. After a while examining the case, I did change it back and the vars finally reach it's destination!

So what means each one of this headers, how it changes the way data is exchanged?

Answer 1

x-www-form-urlencoded means it escapes some special characters and make the whole datapackage (form) one single string. octet-stream i never seen this format but my raw guess is that its a stream of 8 bit chunks of data.

Answer 2

application/x-www-form-urlencoded is the content-type for the standard way of encoding form data (which is also used in query strings).

application/octet-stream is the content-type for "some bytes of date, in no particular format" (often it is used for "I don't know what this is" and sometimes for "I don't want the browser to know what this is" when Content-Disposition should be used instead).

The header doesn't change how the data is exchanged, it just informs the recipient of what format the data is in.

If PHP is told the data is in a format that it doesn't know how to parse then it won't parse it and populate $_POST and friends.