PHP through regular filtering of illegal Chinese characters or characters

Illegal Chinese characters can affect the display and even the execution of programs, and there are some unexpected results. So we need to filter these illegal Chinese characters or characters.
Code as follows

code is as follows

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function Normalizetext ($text, $length = null) {     $text =\normalizer::normalize ($text, \normalizer:: Form_c);     $text = preg_replace ('/[^\p{l}\p{p}\p{n}\p{s}\p{zs}]/u ', "", $text);     $text = preg_replace ('/^\p{z}*/u ', "", $text);     $text = preg_replace ('/\p{z}*$/u ', "", $text);     if ($length!== null) {         $text = mb_substr ($text, 0 , $length, ' utf-8 ');    }     return $text; }