隨機生成字符 可自定義位數，大小寫，去掉類似字符

    /*函數-生成隨機字符串,
    $num,指定生成位數,
    $similar 是否包含類似字符
    $type 字符類型 true 大寫.false 小寫
    */
    function randText($num,$type = false,$similar = false){
        
        //組合
        $chars = array();
        $chars = array_flip(array_merge(range(0,9),range('a','z')));
        if($similar === false){
            
            //去掉類似
            unset($chars[0],$chars[1],$chars[2],$chars[5],$chars[8],$chars['b'],$chars['i'],$chars['o'],$chars['q'],$chars['s'],$chars['u'],$chars['v'],$chars['v']);
        }
        //進行遍歷
        for($i = 0; $i < $num; $i++ ){
            
            $str .=array_rand($chars);
        }
        
        if($type === true){
            
            $str = strtoupper($str);

        }
        return str_shuffle($str);
    }