Php foreach references assignment, foreach references assignment

Php foreach references assignment, foreach references assignment

When writing code, it is found that the php foreach reference assignment will lead to unexpected behavior.

Sample Code:

  <?php         $arr = array('a','b','c');        foreach($arr as $k=>&$v)         {        }                print_r($arr);         foreach($arr as $k=>$v)        {             }                print_r($arr);   ?> 

Output result: Array ([0] => a [1] => B [2] => c) array ([0] => a [1] => B [2] => B) Find the information and find the cause. In fact, after the first foreach ends, the reference of the last element $ v in the array $ arr is still retained. In the second foreach loop, it is actually to assign the second foreach to the third element of the array $ arr for execution. The changes to the array $ arr each time are as follows: the first time: array ([0] => a [1] => B [2] => a) Second Time: array ([0] => a [1] => B [2] => B) Third time: array ([0] => a [1] => B [2] => B. To avoid this situation, you can cancel the reference: unset ($ v) after the first foreach is completed ). However, to avoid unexpected results, use foreach to reference values with caution.