PHP实现过滤掉非汉字字符只保留中文字符

<?php$str = "a 1b 2b＜中文＞。xxyy字符";//转换 GB2312 -> UTF-8$str = mb_convert_encoding($str, 'UTF-8', 'GB2312');preg_match_all('/[/x{4e00}-/x{9fff}]+/u', $str, $matches);$str = join('', $matches[0]);//转换 UTF-8 -> GB2312$str = mb_convert_encoding($str, 'GB2312', 'UTF-8'); echo $str; //输出 中文字符?>