<?phpfunction buildRandomString($type=1,$length=4){?if（$type==1){ $chars=join("",range(0,9));?}elseif($type==2){ $chars=join("",array_merge(range("a","z"),range("A","Z")));??}elseif($type==3){? ? $chars=join("",array_merge(range("a","z"),range("A","Z"),range(0,9)));?}?if（$length>strlen($chars)){ exit("字符串長度不夠");?}?$chars=str_shuffle($chars);?return substr($chars,0,$length);}提示第三行有錯誤