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Skip to comments (7) PHP foreach pitfall
Posted by Erik on Jan 27 2006 @ 15:32  :: 3842 unique visits

Today I encountered this stupid foreach pitfall. I was doing some stuff with an array, adding elements, changing the internal order of the array. And somehow all the time the last element of the array seemed bugged. It's value always equaled that of the element before it. Took me some time to figure this one out:
CODE: PHP
$foo = array(12, 42, 1337);

foreach ($foo as &$bar) {
  ; // do nothing to change the array
}

foreach ($foo as $bar) {
  ; // do nothing to change the array
}

print_r($foo); // this will print array(12, 42, 42)
 

The second foreach loop uses the same $bar variable. But the first loop declared it as a reference. So instead of using $bar in second loop I was using the last element of $foo because $bar was still referencing to it.
I hope that by posting this here I save some people from falling into the same pitfall.

7 comments posted so far
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1. On Jan 29 2006 @ 09:36 dustin wrote:

I thought everyone knew this! ;]

I don't use foreach, usually.

2. On Jan 29 2006 @ 11:03 Buzzard wrote:

I've encountered that before, was a PITA to figure out why :-)

I think PHP should scope variables better too (like C), $bar should only be defined inside each foreach loop (unless you were using it outside of the loop)

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