.. _alias-replace-class:

Alias Replace Class
===================
.. meta::
	:description:
		Alias Replace Class: When a class is defined before an alias, with ``use``, it used to yield a fatal error.
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	:twitter:site: @exakat
	:twitter:title: Alias Replace Class
	:twitter:description: Alias Replace Class: When a class is defined before an alias, with ``use``, it used to yield a fatal error
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	:og:title: Alias Replace Class
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	:og:description: When a class is defined before an alias, with ``use``, it used to yield a fatal error
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	:og:locale: en

When a class is defined before an alias, with ``use``, it used to yield a fatal error. Since PHP 8.4, and when the alias is in a different block than the definition, it is possible to replace a class with another one. 



While the fatal error has been removed, it now means that a class, local to a namespace, is not always described by its relative name. The class is still distinguisable with its absolute name.

PHP code
________
.. code-block:: php

   <?php
   
   namespace A {
           class xBefore {}
   }
   
   namespace A {
       use y as xAfter;
       use y as xBefore;
       class y {}
   
     print get_class(new y);    
   }
   
   
   namespace A {
           class xAfter {}
   }
   
   ?>

Before
______
.. code-block:: output

   PHP Fatal error:  Cannot use y as xBefore because the name is already in use s/aliasReplace.php on line 10
   
   Fatal error: Cannot use y as xBefore because the name is already in use s/aliasReplace.php on line 10
   

After
______
.. code-block:: output

   A\y


PHP version change
__________________
This behavior changed in 8.4


Error Messages
______________

  + `Cannot use%s %s as %s because the name is already in use <https://php-errors.readthedocs.io/en/latest/messages/cannot-use%25s-%25s-as-%25s-because-the-name-is-already-in-use.html>`_