Huge memory usage with concatenation using . instead of .=
| Bug #44069 | Huge memory usage with concatenation using . instead of .= | |||||||||||||
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| Submitted: | 2008-02-07 13:39 UTC | Modified: | 2008-02-14 15:20 UTC |
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| From: | frode dot guldberg at exense dot com | Assigned: | dmitry (profile) | |||||||||||
| Status: | Closed | Package: | Performance problem | |||||||||||
| PHP Version: | 5.2.5 | OS: | * | |||||||||||
| Private report: | No | CVE-ID: | None | |||||||||||
[2008-02-07 13:39 UTC] frode dot guldberg at exense dot com
Description:
------------
In a for-loop I concatenate two strings. If I at the same time fill a relatively small array, I get a huge memory consumption. This only happens if I concatenate the two strings using '.'. If I use '.=' the memory usage is as expected.
Reproduce code:
---------------
<?php
$string = str_repeat('This is a teststring.', 50);
echo 'Length: '.strlen($string).'<br>';
echo 'Memory Before:'.memory_get_usage(true).'<br>';
for($i = 1; $i <= 2000; $i++)
{
// $newstring .= $string; //This uses an expected amount of mem.
$newstring = $newstring . $string; //This uses very much mem.
for($j = 1; $j <= 10; $j++)
{
$array[] = 'test';
}
}
echo 'Memory After:'.memory_get_usage(true).'<br>';
echo 'Total Length of String: '.strlen($newstring).'<br>';
?>
Expected result:
----------------
Length: 1050
Before:262144
After:4456448
Length: 2100000
Actual result:
--------------
Length: 1050
Before:262144
After:161742848
Length: 2100000
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[2008-02-13 18:25 UTC] jani@php.net
[2008-02-14 14:49 UTC] dmitry@php.net