.. _passing-non-callable-strings-is-deprecated-since-8.4:

Passing non-callable strings is deprecated since 8.4
----------------------------------------------------
 
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		Passing non-callable strings is deprecated since 8.4: xml_set_processing_instruction_handler() requires a valid method to be passed.
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Description
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xml_set_processing_instruction_handler() requires a valid method to be passed. Closure, first class callable, and other callable structures are possible. When using a string, make sure it references an existing function name.

Example
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.. code-block:: php

   <?php
   
   // empty string is not a valid callable
   xml_set_processing_instruction_handler($parser, '');
   
   // This cannot be a valid function name
   xml_set_processing_instruction_handler($parser, '123foo');
   
   ?>

Solutions
_________

+ Use a valid function name: non empty string, and a valid name format.

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>`_.