.. _cannot-use(...)-variables-in-constant-expression:

Cannot use(...) variables in constant expression
------------------------------------------------
 
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		Cannot use(...) variables in constant expression: It is possible to have closures in a constant, since PHP 8.
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	:og:title: Cannot use(...) variables in constant expression
	:og:description: It is possible to have closures in a constant, since PHP 8
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Description
___________
 
It is possible to have closures in a constant, since PHP 8.5. Such closure must be static, so that it does not include the current object with ``$this``. It also cannot use the ``use`` clause, as the definition of the closure is outside an execution context: there are no available variables to import in the closure.

Example
_______

.. code-block:: php

   <?php
   
   class X {
       const MY = static function () use ($a) { return 1;};
   }
   
   ?>

Solutions
_________

+ Remove the ``use`` clause of the closure.
+ Move the closure inside a method.

Related Error Messages
______________________

+ :ref:`closures-in-constant-expressions-must-be-static`

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>`_.