ID: 35258
Updated by: [EMAIL PROTECTED]
Reported By: [EMAIL PROTECTED]
-Status: Open
+Status: Wont fix
Bug Type: Documentation problem
Operating System: Linux
PHP Version: 4.4.1
New Comment:
The pcre extension API (used by preg_*() functions, the new filter
extension,..) cache compiled regexes, but since PHP xx (I don't
remember the version.. :) ), that cache has a limit.
So memory usage won't grow indefinetely, it will "just" cache 4096
regexes (by default).
I don't think this should be documented. PHP users don't really want to
know about internal stuff.
Previous Comments:
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[2005-12-13 11:45:34] [EMAIL PROTECTED]
No doubt. However, the ereg* family of functions does not consume
memory in the way the preg* family of functions does. So this is
actually a documentation problem it seems, re-cateogrizing.
------------------------------------------------------------------------
[2005-12-13 10:45:03] [EMAIL PROTECTED]
This is the same issue as all the other "PHP does not release memory"
reports. The memory reserved is never released during script run. It's
released during shutdown.
------------------------------------------------------------------------
[2005-12-13 09:53:55] [EMAIL PROTECTED]
Your answer is interesting. If I take your example and insert another
var_dump() before the unset() command, like this:
<?php
var_dump(memory_get_usage());
$input = str_pad("", 50000, "foo");
var_dump(memory_get_usage());
$input = preg_replace(";foo;", "", $input);
var_dump(memory_get_usage());
unset($input); // <------------ !!
var_dump(memory_get_usage());
I get these numbers:
$ php test.php
int(15496)
int(65600)
int(115632)
int(15624)
However, there is not benefit in unsetting the return value from
preg_replace else I could remove the call to it anyway.
But maybe the example was bad. Take for example, I want to replace
'foo' with 'bar':
<?php
var_dump(memory_get_usage());
$input = str_pad("", 50000, "foo");
var_dump(memory_get_usage());
$input = preg_replace(";foo;", "bar", $input);
var_dump(memory_get_usage());
$ php test.php
int(15208)
int(65312)
int(115352)
If I want to further work with the value I have no way of saving memory
(I can't really unset the value when I need it).
I also don't quite understand the statement "memory usage doesn't
depend on the length of the data". The numbers are certainly different
when I use small strings.
------------------------------------------------------------------------
[2005-11-17 13:59:29] [EMAIL PROTECTED]
Memory usage doesn't depend on the length of the data.
Try this code:
<?php
var_dump(memory_get_usage());
$input = str_pad("", 50000, "foo");
var_dump(memory_get_usage());
$input = preg_replace(";foo;", "", $input);
unset($input); // <------------ !!
var_dump(memory_get_usage());
?>
------------------------------------------------------------------------
[2005-11-17 12:22:25] [EMAIL PROTECTED]
Description:
------------
preg_replace() doesn't seem to release the memory used to do its
operation.
Simple example using preg_replace():
php -r 'var_dump(memory_get_usage()); $input = str_pad("", 50000,
"foo"); var_dump(memory_get_usage()); $input = preg_replace(";foo;",
"", $input); var_dump(memory_get_usage());'
int(15216)
int(65320)
int(115352)
Simple example using ereg_replace():
php -r 'var_dump(memory_get_usage()); $input = str_pad("", 50000,
"foo"); var_dump(memory_get_usage()); $input = ereg_replace("foo", "",
$input); var_dump(memory_get_usage());'
int(15208)
int(65312)
int(15312)
Maybe this is just a documentation issue, but than it should be noted.
The documentation says that preg_ is faster, which it is, and the
documentation somewhere mentiones a regex cache, but it doesn't say
that the amount of memory grows by the size of the input sring.
It's an interesting behaviour which should be considered when memory is
an issue.
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Edit this bug report at http://bugs.php.net/?id=35258&edit=1
