Get "Content-Type" header of request in PHP

Question

I'm implementing a REST service in PHP. This service should be able to support multiple input and output formats (JSON, XML). For that reason I want to check the request headers "Accept" and "Content-Type" for the type of content sent and requested by the client.

Accessing the "Accept" header is a simple as using $_SERVER['HTTP_ACCEPT']. But accessing the "Content-Type" header seems to be a difficult task. I searched the PHP documentation and the web, but the only solution offered was the use of the PHP function apache_request_headers() which is only supported when PHP is installed as an Apache module, which is not true in my case.

So my question now: How can I access the header "Content-Type" of a request?

Answer 1

Normal (GET) requests do not have a Content-Type header. For POST requests it would appear as $_SERVER["CONTENT_TYPE"], with a value like multipart/form-data or application/x-www-form-urlencoded.

This is mandated by the CGI/1.1 specification: http://www.ietf.org/rfc/rfc3875.

Answer 2

You'll need to manually instruct Apache to supply the Content-Type header (plus any other headers you want).

Pop something like this in your .htaccess file or virtual host:

RewriteEngine on RewriteRule .* - [E=HTTP_CONTENT_TYPE:%{HTTP:Content-Type},L] 

And voila, you just synthesised your very own $_SERVER['HTTP_CONTENT_TYPE']!

Edit:

I assume you're running PHP as CGI with Apache so you can use verbs other than GET and POST, as most rest services do. If you're using another web server or largely unheard-of PHP SAPI, you'll need to use a similar trick; PHP as CGI simply doesn't have access to request headers outside the contents of $_SERVER, no matter what other mechanisms you use - $_ENV, apache_request_headers(), even the classes in the php_http extension will all be empty.