php code not working fully

<?php

    //connecting to database

    $db = mysql_connect("localhost","root","youmint") or die(mysql_error());



    //selecting our database

    $db_select = mysql_select_db("Nikhil", $db) or die(mysql_error());



    //Retrieving data from html form

    $firstname = $_POST['firstname'];

    $lastname = $_POST['lastname'];

    $mobilenumber = $_POST['mobilenumber'];

    $age = $_POST['age'];

    $gender = $_POST['gender'];

    $address = $_POST['address'];

    $city = $_POST['city'];

    $pin = $_POST['pin'];



    //for mysql injection (security reasons)

    $firstname1 = mysql_real_escape_string($firstname1);

    $lastname1 = mysql_real_escape_string($lastname1);

    $mobilenumber1 = mysql_real_escape_string($mobilenumber1);

    $age1 = mysql_real_escape_string($age1);

    $gender1 = mysql_real_escape_string($gender1);

    $address1 = mysql_real_escape_string($address1);

    $city1 = mysql_real_escape_string($city1);

    $pin1 = mysql_real_escape_string($pin1);





    // inserting data into database

    $register = mysql_query( "INSERT INTO Registration ( firstname , lastname , mobilenumber , age , gender , address , city , pin ) VALUES ( '$firstname' , '$lastname', '$mobilenumber' , '$age' , '$gender' , '$address' , '$city' , '$pin' ");

    if($register) {

    echo "Registration Successfull";

    }

    else {

    echo "There was an error";

    }

    ?>