智享笔记 $str = 'example![[坏笑]](http://img.t.sinajs.cn/t4/appstyle/expression/ext/normal/50/pcmoren_huaixiao_org.png)
';
$filtered = preg_replace('/[\x{10000}-\x{10FFFF}]/u', '', $str);
var_dump($filtered); // string(7) "example"
$str = 'example';
$filtered = preg_replace('/[\x{10000}-\x{10FFFF}]/u', '', $str);
var_dump($filtered); // string(7) "example"
