будет ли правильно писать такой код ???PhP

Вот код php

function sing_up_user()
{
    if(isset($_POST['sing_up_user_name']) and isset($_POST['sing_up_user_pass']) and isset($_POST['sing_up_user_email']))
    {
        if(mysqli_num_rows(mysqli_query(mysqli_connect("localhost", "root", ""), 
        "SELECT user_name FROM user.all_user WHERE user_name =  \"". $_POST['sing_up_user_name']."\" "  )) == 0)
        {
            if(mysqli_query(mysqli_connect("localhost", "root", ""),
            "INSERT INTO user.all_user VALUES( ".mysqli_num_rows(mysqli_query(mysqli_connect("localhost", "root", "", "user"),
            "SELECT * FROM user.all_user ")).", \"".$_POST['sing_up_user_name']."\", \"".$_POST['sing_up_user_pass']."\" , \"".$_POST['sing_up_user_email']."\" ,\"0\" , NOW(),\"".$_SERVER['REMOTE_ADDR']."\" )"))
            {
                if(isset($_POST['sing_up_remember']) || $_POST['sing_up_remember'] == "on" )
                {
                    setcookie("UNID", $_POST['sing_up_user_name'] , time()+3600*24*14 , "/");
                    setcookie("SID", $_POST['sing_up_user_pass'] , time()+3600*24*14, "/" );
                    setcookie("SID", $_POST['sing_up_user_email'] , time()+3600*24*14, "/" );
                    setcookie("UID", mysqli_fetch_row(mysqli_query(mysqli_connect("localhost", "root", ""),
                    "SELECT user_id, user_name, user_pass FROM user.all_user WHERE user_name RLIKE \"".$_POST['sing_up_user_name']."\" AND `user_pass` RLIKE \"".$_POST['sing_up_user_pass']."\" "  ))[0] , time()+3600*24*14 , "/");
                    mysqli_close(mysqli_connect("localhost", "root", ""));
                    return true;
                }
                else
                {
                    $_SESSION['UNID'] = $_POST['sing_up_user_name'];
                    $_SESSION['SID'] = $_POST['sing_up_user_pass'];
                    $_SESSION['UID'] = mysqli_fetch_row(mysqli_query(mysqli_connect("localhost", "root", ""),
                    "SELECT user_id, user_name, user_pass FROM user.all_user WHERE user_name RLIKE \"".$_POST['sing_up_user_name']."\" AND `user_pass` RLIKE \"".$_POST['sing_up_user_pass']."\" "  ))[0];
                    mysqli_close(mysqli_connect("localhost", "root", ""));
                    return false;
                }
            }
            else 
            {
                mysqli_close(mysqli_connect("localhost", "root", ""));
                return false;
            }
        }
        elseif(mysqli_num_rows(mysqli_query(mysqli_connect("localhost", "root", ""), 
        "SELECT user_name FROM user.all_user WHERE user_name RLIKE \"".$_POST['sing_up_user_name']."\"")) != 0)
        {// username already exists 
            mysqli_close(mysqli_connect("localhost", "root", ""));
            return false;
        }
        else
        {
            mysqli_close(mysqli_connect("localhost", "root", ""));
            return false;
        }
    }
    else
    {
        mysqli_close(mysqli_connect("localhost", "root", ""));
        return false;
    }
}//func sing_up_user end 

• это что-то подобное регистрации))

Насколько подобный код ,только в большом маштабе, будет нагружать сервер ??

Буду рад каждому ответу ))