Description:
------------
The PHP manual now states, that strings are limited to 2GB. However in test 
script, I specify a memory limit to 800MB. I wrote a PHP application where memory 
usage is growing over time. Unfortunately the size of a single string variable 
doesn't  exceed memory limit of 300-400MB and my test stops. Testing my script on 
5.4.17,18,19 and  5.3.10 of PHP versions, but any of this versions don't 
supported  my memory limit or 2GB memory.

Test script:
---------------
<?php
ini_set('memory_limit', '800M');
$string = '1234567890';
$strb = '';
for ($i = 0; $i < 1000000; $i++)
    $strb .= $string;
$arr = array();
$i = 0;
$testType = 'string'; //'array'
while (1) {
    $i++;
    if ('string' == $testType) {
        error_log((strlen($string) / 1000000) . ' - ' .
                (memory_get_usage() / 1000000));
    } else {
        $arr[] = $strb . $i;
        error_log((strlen($string) / 1000000) . ' - ' .
                (memory_get_usage() / 1000000));
    }
    error_log((count($arr)) . ' - ' . (memory_get_usage() / 1000000)); }

Expected result:
----------------
Memory usage grow to about 800MB.

Actual result:
--------------
Memory error of 300-400MB. So the memory usage does not continually grow to 800MB.