[php-src] Issue #20439: xml_set_default_handler() does not properly handle special characters in attributes when passing data to callback

Issue: https://github.com/php/php-src/issues/20439 Author: bawolff ### Description The following code: ```php <?php $x = xml_parser_create_ns( 'utf-8' ); xml_set_default_handler( $x, function( $p, $data ) { echo $data; } ); xml_parse( $x, "<foo attr1='\"&lt;&quot;' attr2=\"&quot;&lt;\"></foo>" , true ); ``` Resulted in this output: ``` <foo attr1=""<"" attr2=""<"></foo> ``` But I expected this output instead: ``` <foo attr1="&quot;&lt;&quot;" attr2="&quot;&lt;"></foo> ``` Note: This requires you to compile php without expat. If expat support is compiled in, then the bug does not happen. Basically, attributes with " or < get mangled resulting in invalid XML. ### PHP Version ```plain PHP 8.4.14 (cli) (built: Nov 8 2025 21:25:55) (NTS) Copyright (c) The PHP Group Built by Debian Zend Engine v4.4.14, Copyright (c) Zend Technologies with Zend OPcache v8.4.14, Copyright (c), by Zend Technologies ``` ### Operating System _No response_