Two foreach loops with same variable names break the order of elements

Question

Here is my code:

foreach($datawallright[\'adds\'] as &$ad){
    $ad[\'img\'] = get_ad_pic_url($this->em->getReference(\"models\\MmAds\",$ad[\'id\']),\'         


        

Answer 1

What happened is that the first loop iterates by reference, so when the second attempts to assign "the current item" to $ad it actually updates your array contents in addition to updating $ad.

The simplest fix is to add an unset ($ad) immediately after the first foreach so that PHP will not consider the name $ad a reference from that point onward.

The need to do this (or else suffer from hidden updates to the reference later on) is one of the ugliest things that can bite you in PHP; personally I am very religious about appending an unset after iterating by reference, even if that's the last statement in a function.