FSBSchedule Login (PHP)

<?php
$link = new mysqli(
    "foo",
    "bar",
    "blargh",
    "loremIpsumDolorSitAmetAmet"
);

if(!get_magic_quotes_gpc()) {
    $email = addslashes($_POST['email']);
    $password = addslashes(hash("sha-512", $_POST['password']));
    if(isset($_POST['fsb_email']) {
        $fsb_email = addslashes($_POST['fsb_email']);
    }
}

if(ctype_alpha($_POST['lastName']) || ctype_alpha($_POST['firstName'])) {
    $lastName = $_POST['lastName'];
    $firstName = $_POST['firstName'];
} else {
    exit("Names must contain only letters.");
}

if(!isset($_POST['submit'])) {
    exit("No form data was submitted (HTTP post parameter \"submit\" must be sent).");
} elseif(!$_POST['lastName'] || !$_POST['firstName'] || !$_POST['email'] || !$_POST['password'] || !$_POST['password_confirm']) {
    exit("Missing required form values.\n");
}

//$email = addslashes($_POST['email']);
if(mysqli_num_rows(mysqli_query($link, "SELECT email FROM users WHERE email = $email")) != 0) {
    exit("The email provided is already registered.\n");
}

if($_POST['password'] != $_POST['password_confirm']) {
    exit("The provided passwords did not match\n");
}
// Crypt salt using SHA-512: $6$rounds=26873856$Lorem ipsum dolor sit amet amet.$
//$password = addslashes(hash("sha-512", $_POST['password']));

if(isset($_POST['fsb_email'])) {
    mysqli_query($link, "INSERT INTO users (email, fsb_email, password, LastName, FirstName) VALUES($email, $fsb_email, $password, $lastName, $firstName)");
} else {
    mysqli_query($link, "INSERT INTO users (email, password) VALUES($email, $password)");
}

print("Successfully registered.\n");
?>