Section 5.20. Setting the Content Type

5.20. Setting the Content Type

You have to set the content type for your POST data before you send the request. Then, when the request is sent, the server will get the request URL, the POST data, and the type of data it should expect. Anytime you need to tell a server something about a request, you'll use a request header.

Let's see how we can set a request header for the Break Neck request:

 function submitOrder() {   var phone = document.getElementById("phone").value;   var address = document.getElementById("address").value;   var order = document.getElementById("order").value;   var url = "placeOrder.php  ";   request.open("POST", url, true);   request.onreadystatechange = showConfirmation;setRequestHeader() allows you to add information to the request, usually intended for use by the server.   request.setRequestHeader("Content-Type","Content-Type" is the name of the header...           "application/x-www-form-urlencoded");...and this is the value for that request header.This tells the server the data is encoded like it would be in a request URL, just as if the data came as part of a GET request.     request.send("phone=" + escape(phone) +                "&address=" + escape(address) +                "&order=" + escape(order)); } 

Frequently Asked Questions?

Q:	So a request header is sent to the server along with the request?
A:	Yes. Any request headers are part of the request. In fact, the web browser sets some request headers automatically, so you're really just adding a request header to the existing ones.
Q:	And "Content-Type" is used to tell the server what kind of POST data we're sending?
A:	You've got it. In this case, we're using name/value pairs, and the content type for that is "application/x-www-formurlencoded". That particular type tells the server to look for values like it would get from a normal form submission.
Q:	Are there other content types I should know about?
A:	There sure are. In the next chapter, we'll look at the content type for XML. There are tons more, and you can simply Google for "HTTP Content-Type" to find various lists online for all sorts of different file and content types.