.. _cannot-use-list-as-key-element:

Cannot use list as key element
------------------------------
 
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		Cannot use list as key element: Since PHP 7.
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	:og:title: Cannot use list as key element
	:og:description: Since PHP 7
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Description
___________
 
Since PHP 7.1, ``foreach`` can destructure the value of each entry with ``list()`` (or its short ``[]`` syntax): ``foreach ($array as $key => list($a, $b))``. The key part, on the other hand, is always a single target: a variable, a property, or an array offset. It cannot itself be a ``list()`` pattern, since a single array key has nothing to be destructured into several variables.

Example
_______

.. code-block:: php

   <?php
   
   $array = [['a', 'b'], 'c', 'd'];
   
   foreach ($array as list($key) => $value) {
   }
   
   ?>


Literal Examples
****************
+ Cannot use list as key element

Solutions
_________

+ Use a plain variable for the key, and only destructure the value with ``list()``.

Related Error Messages
______________________

+ :ref:`cannot-use-list()-as-standalone-expression`

Changed Behavior
________________

This error may appear following an evolution in behavior, in previous versions. See ` <https://php-changed-behaviors.readthedocs.io/en/latest/behavior/.html>`_.