Why does is_array() leak memory in PHP?

Question

According to my xdebug output, is_array() leaks the amount of memory that gets passed to it as an argument. If I pass it a large array, it leaks a ton of memory just in order to check if it's an array.

Is there a workaround for this?

   17.4313   21858520   +70004                   -> is_array() [...]/app/app_model.php:526

Here's the code snippet that causes the leak:

        $ret = $this->behaviors[$b[$i]]->afterFind($this, $results, true);
        if (is_array($ret)) {
            $results = $ret;
        }

I'm running this on Linux (Ubuntu 9.04)

PHP: 5.3.2

xdebug: 2.0.5

uname -a gives me this:

Linux linux8 2.6.28-19-server #64-Ubuntu SMP Wed Aug 18 21:57:33 UTC 2010 i686 GNU/Linux

I think you forgot to specify PHP version and your code, which should be relevant to this leak. insertPHPJoke() — meder omuraliev
– meder omuraliev, Commented Sep 8, 2010 at 14:58
What do you mean "leak memory"? The memory is not reclaimed after the call? — Artefacto
– Artefacto, Commented Sep 8, 2010 at 15:09
Is I cannot reproduce it here: have you got xdebug.collect_params enabled, and what happens if you disable it? — Wrikken
– Wrikken, Commented Sep 8, 2010 at 15:55
After checking: no, collect params doesn't seem the culprit, and I cannot reproduce it. Some version numbers (PHP & xdebug), OS & a specific test script could be required. — Wrikken
– Wrikken, Commented Sep 8, 2010 at 16:03
Just look in the source code if you want to know what happens: type.c:201 PHP 5.3.2 — Lekensteyn
– Lekensteyn, Commented Sep 8, 2010 at 17:04

xtofl · Accepted Answer · 2010-09-09 14:43:39Z

5

My first reaction:

Select isn't broken.

My second reaction:

You can conclude three things:

a widely spread piece of software (is_array) is broken - You are the first one to notice
xdebug is broken reports a leak where there is none
xdebug and PHP don't work together nicely as it concerns memory management

A widely spread and used function is most often not the problem. Try to narrow down the occurence of the 'xdebug leak report' by running simpler code:

$arr = array_fill( 0, 10000, "content" );
$mallocbytes=true;// set to true to get process 
$usage=memory_get_usage(!$mallocbytes);
for( $i=0; $i!=1000000; $i=$i+1) { 
   is_array($arr); 
   $newusage=memory_get_usage(!$mallocbytes);
   if( $newusage != $usage ) {
      print( "diff after $i'th is_array: ".($newusage-$usage)."\n" );
   }
   $usage=$newusage;
}

Take a look at the actual memory consumption of your PHP runtime. I bet it won't grow.

edited Sep 9, 2010 at 14:43

answered Sep 9, 2010 at 8:15

xtofl

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1 Comment

MapDot Over a year ago

After running your example, I believe that the problem is in xdebug and not in the PHP runtime.

Beth · Accepted Answer · 2010-09-08 23:46:47Z

0

http://php.net/manual/en/function.gettype.php may be a suitable work-around. The best path is to submit a patch that fixes the bug, but that may be outside the scope of your contract.

answered Sep 8, 2010 at 23:46

Beth

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