Description:
------------
Output buffering doesn't respect the maximum limit as set in php.ini in php 5.1.4 plus some earlier versions.
output_buffering=xxx

In fact it is possible to go well past the limit and consume the entire memory allocated to the script by memory_limit causing the script to halt.


snippet from php.ini -
If you wish to limit the size of the buffer
; to a certain size - you can use a maximum number of bytes instead of 'On', as
; a value for this directive (e.g., output_buffering=4096).

Reproduce code:
---------------
ini_set("zlib.output_compression",0);
ini_set("max_execution_time",5);
// set this to larger than your output_buffering=xxx limit
ini_set("memory_limit",'3M'); 

echo 'Maximum buffer size as set in php.ini output_buffering: ',
    $limit = ini_get("output_buffering"),
    '<br />';

echo '<br />','Starting OB test...','<br />';
ob_start();
    // fill up the buffer 10 bytes beyond the supposed limit
    for($i=0;$i<($limit+10);$i++) { echo 'a'; }
    $size = ob_get_length();
ob_end_flush(); 

Expected result:
----------------
Expected the output buffer to respect the maximum bytes cap as set out in php.ini output_buffering=xxxx

Actual result:
--------------
The buffer keeps on growing past the set limit, until it fills the memory_limit or max_execution_time limits and terminates the script.