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Bug #20844 "array()" doesn't free memory
Submitted: 2002-12-05 16:55 UTC Modified: 2002-12-06 01:23 UTC
From: busia at tiscali dot it Assigned:
Status: Not a bug Package: Scripting Engine problem
PHP Version: 4.3.0RC2 OS: Redhat 7.0
Private report: No CVE-ID: None
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From: busia at tiscali dot it
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 [2002-12-05 16:55 UTC] busia at tiscali dot it 
If I run this script:

<?
ini_set('memory_limit','100M');
echo "a";
$array=array();
for($i=0; $i<=500000; $i++) $array[]="pippoplu";
echo "b\n";
sleep(15);
$array=array();
echo "c\n";
sleep(15);
for($i=0; $i<=300000; $i++) $array[]="pippoplu";
echo "d\n";
sleep(15);
?>

and I watch the memory usage i see:
after the 'echo "a"': memory usage increases and it reaches 64MB (all is ok)
after the 'echo "b"': memory usage is 64MB (all is ok)
after the 'echo "c"': memory usage is 62MB (not ok)
after the 'echo "d"': memory usage remains 62MB (not ok)

Why '$array=array();' don't free the memory used by $array?
and why the memory don't increases when between ' echo "c"' and 'echo "d"'?

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 [2002-12-05 17:01 UTC] busia at tiscali dot it 
If I add the line
unset($array);
before
$array=array(); (line: 8)
the result remains the same.
 [2002-12-05 17:06 UTC] busia at tiscali dot it 
I have reproduced the problem also on an ther server (this server uses redhat 7.2)
 [2002-12-06 01:23 UTC] derick@php.net 
This is not at all a problem in PHP, but rather a UNIX behavior. While dumping the real in-use memory by PHP with help of xdebug, you see that it clearly frees the memory internally:

$ php bug20884.php 
35728a
38133048b
50192c
23733064d

modified script:

<?php
xdebug_start_trace();
ini_set('memory_limit','100M');
echo xdebug_memory_usage();
echo "a\n";
$array=array();
for($i=0; $i<=500000; $i++) $array[]="pippoplu";
echo xdebug_memory_usage();
echo "b\n";
sleep(15);
$array=array();
echo xdebug_memory_usage();
echo "c\n";
sleep(15);
for($i=0; $i<=300000; $i++) $array[]="pippoplu";
echo xdebug_memory_usage();
echo "d\n";
sleep(15);
?>

Nog a bug in PHP -> bogus
 
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