密码动态生成(复杂、纯英文、纯数字)

function randpw($len=8,$format='ALL'){
    $is_abc = $is_numer = 0;
    $password = $tmp ='';    
    switch($format){
        case 'ALL':
            $chars='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
        break;
        case 'CHAR':
            $chars='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';
        break;
        case 'NUMBER':
            $chars='0123456789';
        break;
        default :
            $chars='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
        break;
    }
    mt_srand((double)microtime()*1000000*getmypid());

    //组合字符串
    while(strlen($password)<$len){
        //随机字符或数字
        $tmp =substr($chars,(mt_rand()%strlen($chars)),1);
        //判断是否出现数字了
        if(($is_numer <> 1 && is_numeric($tmp) && $tmp > 0 )|| $format == 'CHAR'){
            $is_numer = 1;
        }
        //判断是否出现字符了
        if(($is_abc <> 1 && preg_match('/[a-zA-Z]/',$tmp)) || $format == 'NUMBER'){
            $is_abc = 1;
        }
        //连接
        $password.= $tmp;
    }
    //判断条件是否符合，或者重新生成
    if($is_numer <> 1 || $is_abc <> 1 ||  empty($password) ){
        $password = randpw($len,$format);
    }
    
    return $password;
}

for($i = 0 ; $i < 10; $i++){
    echo randpw(8,'NUMBER');
    echo "<br>";
}