Is it necessary to include extra headers when making an XmlHttpRequest POST?

When initiating an XmlHttpRequest POST connection

var http = new XMLHttpRequest();
http.open("POST", url, true);

Some suggest adding the following headers before sending the request:

http.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
http.setRequestHeader("Content-length", params.length);
http.setRequestHeader("Connection", "close");

Do these additional headers need to be included when using an Apache+PHP server? Surprisingly, it seems to work without them on my server.

Answer №1

When sending data without headers, your code works well because the default post content-type is

application/x-www-form-urlencoded
. This can be verified in the console. However, if you are including a file in your request, you must explicitly set the content type to multipart/form-data for the server to accept it. Additionally, receiving proper headers in the response is crucial for the client to correctly interpret the type of response. For example, if a JSON response is expected but headers are not specified as APPLICATION/JSON, the response may be mistakenly interpreted as text/html.

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