Description:
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I have written a mb_trim function in php which uses ereg_replace to trim strings in the same manner as trim() does.

The function is available at http://php.net/manual/en/ref.mbstring.php
Under the heading 'phpnet at rcpt dot at - 19-Aug-2010 02:46'

Using the string excerpt from our production environment (http://pastebin.com/wmyjPmBV), ereg_replace appears to enter some sort of recursive loop, in my environment it takes 100% cpu for 20 minutes before finally returning the correct result.

When the section which reads: array( "\s","\t","\n","\r", "\0", "\x0B" )

...is changed to array( "\s", "\0", "\x0B" ) then ereg_replace returns promptly with the correct result.



Test script:
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The function is available at http://php.net/manual/en/ref.mbstring.php
Under the heading 'phpnet at rcpt dot at - 19-Aug-2010 02:46'

It is also available here:
http://pastebin.com/CCpaVXay

The (serialized) string that causes the problem is:
s:488:"<I>Swans	</I>																						Wisely moving from the middle of July to the middle of autumn, this indoor, forward-thinking avant-rock weekend brings together all sorts of fiercely experimental noisemakers, from psychedelic-folk to death metal, with a hotly anticipated headline set from Michael Gira's New York noise inspiration Swans. Don't expect many stony-faced rock nerds, though. The organisers serve tea and cake throughout and they're promising other fun and games this year.";


It is also available for download here:
http://pastebin.com/wmyjPmBV

You can execute the script with the following syntax:
<?php mb_trim( $string );

Expected result:
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PHP will return the correct result quickly.

Actual result:
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PHP will run at 100% CPU for 20 minutes.