随机生成字符 可自定义位数，大小写，去掉类似字符

    /*函数-生成随机字符串,
    $num,指定生成位数,
    $similar 是否包含类似字符
    $type 字符类型 true 大写.false 小写
    */
    function randText($num,$type = false,$similar = false){
        
        //组合
        $chars = array();
        $chars = array_flip(array_merge(range(0,9),range('a','z')));
        if($similar === false){
            
            //去掉类似
            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'],$chars['v']);
        }
        //进行遍历
        for($i = 0; $i < $num; $i++ ){
            
            $str .=array_rand($chars);
        }
        
        if($type === true){
            
            $str = strtoupper($str);

        }
        return str_shuffle($str);
    }