PHP foreach/reference oddities

Tech Blog :: PHP foreach/reference oddities

Oct 27 '10 4:43pm

Link
Shrt.ct

I encountered this weirdness today with some basic PHP:

Early in the script I had: (note the reference &$nid)

// validate
foreach($nids as $key => &$nid) {
  if (empty($nid)) unset($nids[$key]);
  if (! is_numeric($nid)) unset($nids[$key]);
  $nid = (int) $nid;
}
 
print_r($nids);

Outputs:

Array
(
[0] => 81
[1] => 1199
)

Then later on...

  foreach($nids as $nid) {
    echo $nid;
  }

Outputs:
81
81

If I change the 2nd loop to:

  foreach($nids as &$nid) {
    echo $nid;
  }

then it outputs 81 and 1199 like it should.

Shouldn't as $nid reset the variable so it's no longer a reference?

By Bálint Kléri (not verified) on Sat, 10/30/2010 - 08:17:

I've just encountered this same weirdness, and I remembered this post, so thank you! :)

I've checked the manual of the foreach, and I've found a warning about this behavior:
"Reference of a $value (in your case: $nid) and the last array element remain even after the foreach loop. It is recommended to destroy it by unset()."

By Martin (not verified) on Thu, 03/31/2011 - 06:49:

see explaination here:
http://i-code-today.blogspot.com/2009/02/php-array-foreach-loop-with-ref...