PHP获取字符流中第一个不重复字符的方法

<?phpglobal $result;//Init module if you needfunction Init(){  global $result;  $result = [];}//Insert one char from stringstreamfunction Insert($ch){  global $result;  // write code here  if(isset($result[$ch])){    $result[$ch]++;  }else{    $result[$ch] =1;   }}//return the first appearence once char in current stringstreamfunction FirstAppearingOnce(){  global $result;  foreach($result as $k =>$v){    if($v ==1){      return $k;    }  }  return "#";}