Getting User id to proceed with Login

I am making a small webpage, and I want to extract the user id, so as to check whether the account exists or not. I do this by connecting to a MySQL DB, and checking to see if the account exists. I am very new to all of this, and only know the absolute basics of PHP & MySQL. Here is my login.php:

login.php

    <?php

    $server = "fooServer";
    $user = "foo";
    $pass = "foo";
    $db = "newsContent";                    
    $conn = new mysqli($server, $user, $pass, $db);
    if ($conn->connect_error) 
    {
    die("Connection failed: " . $conn->connect_error);
     } 
?>

<?php 
    $email = $_POST['email']; //Taken from my index.php
    $password = $_POST['password']; //Taken from my index.php

/*I used this so as to extract the id. I then wanted to
proceed with the procedure if the id existed, and alert the user if it didn't*/
    $sql = "SELECT id FROM fooTable WHERE username='$email' && password='$password'";

    if ($conn->query($sql) === TRUE) {
    echo "
    <script>
        alert('Login Successful');
        window.location.href='news.php';
    </script>";
    } else {
        <script>
        alert('Login unuccessful. User account does not exist');
        window.location.href='news.php';
    </script>";
    }
?>

This code may look horrific to experienced programmers, which I understand, but please fire-away with suggestions. Thanks in advance for your help.