PHP 8.2+: mb_convert_encoding(..., 'HTML-ENTITIES') in Html2Text.php breaks bugnote submission via REST API (HTTP 500)

[anthony5301]

Environment

• VEditor: 1.1.2
• MantisBT: 2.28.3 (also reproduced on 2.28.0; present throughout 2.28.x)
• PHP: 8.3.31 (mod_php / Apache)

Summary

With VEditor enabled, submitting a bugnote (or any text VEditor processes)
through MantisBT's REST API fails with HTTP 500 on PHP 8.2+.

Root cause

src/Html2Text.php:54:

$html = mb_convert_encoding($html, "HTML-ENTITIES", "UTF-8");

It will only crash on REST api because api/rest/index.php:

set_error_handler( 'deprecated_errors_handler', E_DEPRECATED );

[pysiek634]

Thank you for reporting the issue. Very few people use this feature and UTF-8 encoding.
Replace this line 54 in Html2Text.php with

			$convmap = [
				0x80,
				0x7FF,
				0,
				0x10FFFF,
				0x10000,
				0x1FFFFF,
				0,
				0x10FFFF,
			];
			$html =  mb_encode_numericentity($html, $convmap, "utf8");

This change will be included in the next version of the plugin.