I just wanted to ask if this is a secure code (doesn't really matter if it's optimal or not)

The code

if(!$_SESSION['logged']){


    if(!$_POST['inputlogin']||!$_POST['inputpassword']){

        require 'cpanellogin.php';

        die();

    }


    else{

        $con=mysqli_connect("localhost","root","","librarydb");

        mysqli_query($con,'SET CHARACTER SET utf8');

        mysqli_query($con,'SET collation_connection = latin2_general_ci');

        $login = $_POST['inputlogin'];

        $password = $_POST['inputpassword'];

        $loginsquery = mysqli_query($con,"SELECT Konta_login, Konta_haslo FROM konta");

        while($row = mysqli_fetch_array($loginsquery))

        {

            $logins[] = $row['Konta_login'];

            $passwords[] = $row['Konta_haslo'];

        }

        $misslogin=0;

        for($i=0;$i<count($logins);$i++){

            if($login==$logins[$i]){

                if(MD5($password)==$passwords[$i]){

                    $_SESSION['logged'] = $logins[$i];

                    require 'cpanel.php';

                    die();

                }

                else{

                    $_POST['logerror'] = "Wrong password";

                    require 'cpanellogin.php';

                    die();

                }

            }

            else{

                $misslogin++;

            }

            if($misslogin==count($logins)){

                $_POST['logerror'] = "Wrong login";

                require 'cpanellogin.php';

                die();

            }

        }

    }

}

haslo means password

konta means accounts