PHP array foreach reference problem

<?php$arr = Array (' 1 ', ' 2 '), foreach ($arr as & $value) {}foreach ($arr as $value) {    var_dump ($value);}

Output

string(1) "1"string(1) "1"

Let's just say it, put it foreach into an assignment.

foreach($arr as &$value) {    //noop}

is roughly

#begin first foreach$value = &$arr[0];//noop$value = &$arr[1];//noop#end foreach

If you print $arr, you will see

array(2) {  [0]=>  string(1) "1" [1]=> &string(1) "2"}

$valuethat is, still $arr[1] the reference (alias)

And then we'll take the second foreach apart.

#begin second foreach$value = $arr[0];//note: 由于$value <=> &$arr[1]， 此时$arr[1]被赋值成为$arr[0]，也就是1var_dump($value);//1$value = $arr[1];//相当于$arr[1] = $arr[1]; 没有实际效果var_dump($value);//1#end foreach

The solution is never to use &

Or honestly follow the official website's instructions, use unset to dereference

  <?php  $arr = array (1, 2, 3, 4);  $arr as & $value) {  $value =  $value * 2;} //$arr is now Array (2, 4, 6, 8) unset (  $value); //break the reference and the last Element?>  span>                 

PHP array foreach reference problem