//生成隨機(jī)字符串function buildRandomString( $type=1, $length=4){    //若不用join，則默認(rèn)以逗號連接    if($type==1){        $chars=join("",range(0,9));//0123456789    }else if($type==2){        //array_merge()把數(shù)組合并，返回的也是數(shù)組        $chars=join("",array_merge(range("a","z"),range("A","Z")));    }else if($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");    }    //字符串順序隨機(jī)打亂    $chars=str_shuffle($chars);    //echo $chars;    return substr($chars,0,$length);}
生成唯一名字
//生成唯一名字function getUniName(){    //microtime(true) 參數(shù)為true，表明是浮點(diǎn)類型    //uniqid(microtime(true),true) 參數(shù)為true，表明位數(shù)擴(kuò)展    return md5(uniqid(microtime(true),true));}
得到文件擴(kuò)展名
//得到擴(kuò)展名function getExt($filename){    $array=explode(".", $filename);    return strtolower(end($array));//end函數(shù)必須傳具體參數(shù)類型，否則會有警告}