assign.byRefForeachExpr

Code example

<?php declare(strict_types = 1);

$array = [1, 2, 3];
foreach ($array as &$item) {
	$item *= 2;
}

$item = 'foo';

Why is it reported?

After a foreach loop that iterates by reference, the loop variable ($item) remains a reference to the last element of the array. Any subsequent assignment to that variable will overwrite the last element of the array, which is almost always unintentional and a common source of bugs in PHP.

In the example above, after the foreach loop, $item still references $array[2]. Assigning 'foo' to $item changes $array[2] from 6 to 'foo'.

How to fix it

Unset the reference variable immediately after the foreach loop:

 <?php declare(strict_types = 1);

 $array = [1, 2, 3];
 foreach ($array as &$item) {
 	$item *= 2;
 }
+unset($item);

 $item = 'foo';