If I remove the recursive part
(?:\\}(?<block>.*?(?:(?0).*?)*?)\\{/(?P=function))?
 from the end of the regex, then it works fine...

The leak is in relation with this
http://bugs.php.net/bug.php?id=49333


Here is a simplyfied example with eight "withoutBlock" tokens:

<?php

ini_set('pcre.backtrack_limit', 40000);
ini_set('pcre.recursion_limit', 1000);

$pattern=
'%
	{(\w+)(?:}
		(.*?(?:(?0).*?)*?)
	{/\1)?}
%usDx';

$test='
{display}
{display}
{display}
{display}
{display}
{display}
{display}
{display}
';

preg_match_all($pattern,$test,$matches,PREG_SET_ORDER);
var_dump($matches);

?>

The basic syntax is:
  {withBlock}block{/withBlock}
or
  {withoutBlock}


As the {withBlock} opener part is of the same structure like the {withoutBlock}, it starts to collect the string after the {withoutBlock} to the backtrace. But for some kind of reason the {withoutBlock} backtrace eats up the memory superexponential, not linear like in the case of {withBlock}.



A measured the memory usage with the simplyfied example. It was not superexponential, just exponential. I think cause I have in this example two capturing groups only, not a lot like in the original code.

tokens	M1[b]	M2[b]	LN(M2)
1	19	22	3,0910
2	53	115	4,7449
3	87	405	6,0039
4	121	1286	7,1593
5	155	3940	8,2789
6	189	11913	9,3854
7	223	35843	10,4869
8	257	107644	11,6204

M1 = 34 * N - 15
R^2 = 1

M2 = exp ( 1,1192 * N + 2,6669 )	
R^2 = 0,9999 for the 3-8 part

Btw. it's funny memory usage.....................

If it is not clear, by the test:

the 8 tokens withBlock (M1) test string is:

$test='
{display}
{display}
{display}
{display}
{display}
{display}
{display}
{display}
{/display}
{/display}
{/display}
{/display}
{/display}
{/display}
{/display}
{/display}
';

and the 8 tokens withoutBlock (M2) test string is:

$test='
{display}
{display}
{display}
{display}
{display}
{display}
{display}
{display}
';

Thank you for taking the time to write to us, but this is not
a bug. Please double-check the documentation available at
http://www.php.net/manual/ and the instructions on how to report
a bug at http://bugs.php.net/how-to-report.php

OK.
If it's not a bug, then what is it?

Did you test it with the command line pcre test tool?  This is unlikely 
to have anything to do with php-specific code.

Ahm, so you mean, this is a pcre memory handling problem, not a php bug? Okay, then where can I report this issue?

(Sorry for the bad English, I'm just med- ...)

"Did you test it with the command line pcre test tool?"

I did not test it.

Ok.

For last, here is my backtrace memory tester. If it's not a bug, then bye bye.

<?php
header('content-type: text/html; charset=utf-8');
header("Cache-Control: no-cache, must-revalidate");
header("Expires: Sat, 26 Jul 1997 05:00:00 GMT");


ini_set('pcre.recursion_limit', 10000);

$kb=1024;
$Mb=1024*1024;

$max_memory_size=50*$Mb;

$pattern=
'%
    {(\w+)(?:}
        (.*?(?:(?0).*?)*?)
    {/\1)?}
%usDx';


if (isset($_POST['test']) && $_POST['test']!='')
{
    ini_set('pcre.backtrack_limit', $max_memory_size);
    if (preg_match_all($pattern,$_POST['test'],$m,PREG_SET_ORDER))
    {
        $a=1;
        $b=$max_memory_size;
       
        while (abs($a-$b)>1)
        {
            $c=(int)(($a+$b)/2);
            ini_set('pcre.backtrack_limit', $c);
            if (preg_match_all($pattern,$_POST['test'],$m,PREG_SET_ORDER))
            {
                $b=$c;
            }
            else
            {
                $a=$c;
            }
        }
       
    }
    ?><div style="float: left; margin: 10px; "><?php
    if (isset($c))
    {
        ?>A fogyasztott memória:<br /><?php echo ($c/$kb); ?>.kb.<br /><?php
    }
    else
    {
        ?>A memória fogyasztás túllépte az engedélyezett kvótát, vagy a minta nem illeszkedik.<br /><?php
    }
    ?><br /><br />A tesztelt szöveg: <br /><pre><?php echo $_POST['test']; ?></pre><?php
    ?></div><?php
   
}

?>
<div style="float: left; margin: 10px;">
<form action="<?php echo $_SERVER['PHP_SELF']; ?>" method="post" enctype="application/x-www-urlencoded; charset=utf-8">
<input type="submit" value="test1" style="vertical-align: top" />
<textarea id="test1" name="test" rows="18">
1.){display}
2.){display}
3.){display}
4.){display}
5.){display}
6.){display}
7.){display}
8.){display}
9.){display}
</textarea>
</form>
</div>

<div style="float: left; margin: 10px;">
<form action="<?php echo $_SERVER['PHP_SELF']; ?>" method="post" enctype="application/x-www-urlencoded; charset=utf-8">
<input type="submit" value="test2" style="vertical-align: top" />
<textarea id="test2" name="test" rows="18">
1.){display}
2.){display}
3.){display}
4.){display}
5.){display}
6.){display}
7.){display}
8.){display}
9.){display}
{/display}
{/display}
{/display}
{/display}
{/display}
{/display}
{/display}
{/display}
{/display}
</textarea>
</form>
</div>