Description:
------------
Hello, 

It's been days I am trying to sort out a problem which pops up when I process a huge XML file.  In "reproduce code" windows is a trivial script which allocates memory by making an array very big.  Assuming a memory_limit of 1024M in <php.ini>, if I don't load the huge XML file, the script crashes as expected with a "memory exhausted" fatal error diagnostic (see expected results window).

However, if I do load my huge XML file with simplexml_load_file(around 300 MB!), the script crashes with a "Out of memory" fatal error diagnostic.  By the way, it doesn't matter if memory_limit is set to 512M or 2048M, the script stumbles on the same "allocated" figure of 332 MB (see actual results windows).

The strangest thing is that before I start swelling the array, the memory usage is almost the same whether ot not simplexml_load_file("VERY_BIG_FILE.XML") is invoked or not.

It looks as if memory allocated by simplexml_load_file() routine is NOT taken into account in overall PHP memory usage and memory limit management.

Thanks in advance for your feedback on that,

Gilbert Musnik


Reproduce code:
---------------
<?php

$flag_xml = true;
$now = Date("Y/m/d - H:i:s");
if ($flag_xml) {
	print ("[ $now ] Before simplexml_load_file\n");
	$f_inp = "VERY_BIG_FILE.xml";  // mine is 300 MB
	
	$ll0 = time();
	$xml = simplexml_load_file ($f_inp);
	$ll1 = time() - $ll0;
	$now = Date("Y/m/D - H:i:s");
	print ("[ $now ] After  simplexml_load_file: $ll1 secondes\n");
	}
else {
	print ("[ $now ] NO simplexml_load_file\n");
	}

$bufrs = array();
$nmax = 150000000;
for ($ii = 0; $ii < $nmax; $ii ++) {
	$bufr = str_repeat ("ABCDEFGHIJ", 1);
	array_push ($bufrs, $bufr);
	$jj = $ii % 1000000;
	if ($jj == 0) {
		$xx = number_format ($ii);
		$qq = number_format (memory_get_usage());
		$memory_limit = ini_get('memory_limit');
		print ("$xx - memory usage=$qq  -  memory_limit=$memory_limit)\n");
		}
	};
?>


Expected result:
----------------
N:\>\php-5.2.6-Win32\php.exe -c \MD_config\php.ini \MD_config\test_mem.php 
[ 2008/06/16 - 18:06:10 ] No simplexml_load_file
0 - memory usage=64,552  -  memory_limit=1024M)
1,000,000 - memory usage=100,259,664  -  memory_limit=1024M)
2,000,000 - memory usage=200,454,016  -  memory_limit=1024M)
3,000,000 - memory usage=304,842,624  -  memory_limit=1024M)
4,000,000 - memory usage=400,842,624  -  memory_limit=1024M)
5,000,000 - memory usage=513,619,840  -  memory_limit=1024M)
6,000,000 - memory usage=609,619,840  -  memory_limit=1024M)
7,000,000 - memory usage=705,619,840  -  memory_limit=1024M)
8,000,000 - memory usage=801,619,840  -  memory_limit=1024M)
9,000,000 - memory usage=931,174,272  -  memory_limit=1024M)
10,000,000 - memory usage=1,027,174,272  -  memory_limit=1024M)

Fatal error: Allowed memory size of 1073741824 bytes exhausted (tried to allocate 35 bytes) in N:\md_config\test_mem.php on line 23

Actual result:
--------------
N:\>\php-5.2.6-Win32\php.exe -c \MD_config\php.ini \MD_config\test_mem.php 
[ 2008/06/16 - 18:05:06 ] Before simplexml_load_file
[ 2008/06/Mon - 18:05:33 ] After  simplexml_load_file: 27 secondes
0 - memory usage=65,472  -  memory_limit=1024M)
1,000,000 - memory usage=100,260,376  -  memory_limit=1024M)
2,000,000 - memory usage=200,454,728  -  memory_limit=1024M)
3,000,000 - memory usage=304,843,336  -  memory_limit=1024M)

Fatal error: Out of memory (allocated 332660736) (tried to allocate 35 bytes) in N:\md_config\test_mem.php on line 23