Passing non-callable strings is deprecated since 8.4

Description

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

<?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');

?>

Alternatives

• 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