Description:
------------
When a POST have an unknwon Content-Type, the php_default_post_reader store the body of the request three times : 

 * In SG(request_info).post_data
 * In SET_VAR_STRINGL("HTTP_RAW_POST_DATA", ...
 * In SG(request_info).raw_post_data

So, getting a 500Mb request body result in a 1.5Gb memory usage, easily triggering a "memory limit exhausted" error.

Known content types are found in main/php_content_types.c and are "application/x-www-form-urlencoded" and "multipart/form-data", so this case is easily triggered.

This fact seems well known as we can read in main/php_content_types.c:59 :

/* for php://input stream:
some post handlers modify the content of request_info.post_data
so for now we need a copy for the php://input stream
in the long run post handlers should be changed to not touch
request_info.post_data for memory preservation reasons
*/

Solving this comment only fix 1/2 of the bug, keeping the body stored in two different locations, but it's a first step.

I only open this ticket to track the history of this issue, I do not really need it to be fixed.