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?>