为什么我的全局变量不起作用？

I am trying to create a signup form that allows potential users to input their first and last name, a username and a password. With this password, I want to use PHP's hash function and some "salts" to make the password secure. To do so, I created a function inside my PHP script to save on redundancy. To accomplish this, I changed variables $connection, $iniSalt, and $endSalt to global variables - thinking this would allow me to use them inside the function addUser(). Can someone tell me what I am doing wrong here? Any advice on how to go about this would be greatly appreciated. Here is my code:

global $connection;
$connection = new mysqli($db_host, $user, $pass, $db);

if ($connection->connect_error) {
    die($connection->connect_error);
}

$query = "CREATE TABLE users (
firstname VARCHAR(32) NOT NULL,
lastname VARCHAR(32) NOT NULL,
username VARCHAR(32) NOT NULL UNIQUE,
password VARCHAR(32) NOT NULL
)";

$result = $connection->query($query);
if (!$result) {
    die($connection->error);
}

global $iniSalt, $endSalt;
$iniSalt = "xb&z*";
$endSalt = "nb!@";

function addUser($conn, $firstname, $lastname, $username, $password) {
    $token = hash('ripemd128', "$iniSalt$password$endSalt");
    $query = "INSERT INTO users VALUES('$firstname', '$lastname', '$username', $token)";
    $result = $connection->query($query);
    if (!$result) {
        die($connection->error);
    }
}

addUser($connection, 'Bill', 'Murray', 'bmurray', 'mysecret');
addUser($connection, 'Jacki', 'Hughes', 'jhughes', 'somepw');

Besides the other answers given in regards to the placement of global, and that I also pointed out in comments about its placement:

Sidenote: Consult my footnotes.

The $token variable is a string and it also must be quoted.

$query = "INSERT INTO users VALUES('$firstname', '$lastname', '$username', $token)";

When your query fires up, you will get a syntax error for it.

So, quote the variable:

$query = "INSERT INTO users VALUES('$firstname', '$lastname', '$username', '$token')";

ripemd128 produces a string, not an integer

http://php.net/manual/en/function.hash.php

ripemd128 32 789d569f08ed7055e94b4289a4195012

Also, if you're planning on going live with this, you'd be better off using password_hash() or the compatibility pack for it.

It's much safer.

References:

PHP 5.5's password_hash() function.
Compatibility pack (if PHP < 5.5) https://github.com/ircmaxell/password_compat/

If and when you do decide to use password_hash() or crypt, it is important to note that if your present password column's length is anything lower than 60, it will need to be changed to that (or higher). The manual suggests a length of 255.

You will need to ALTER your column's length and start over with a new hash in order for it to take effect. Otherwise, MySQL will fail silently.

Footnotes:

Read up on variable scope:

If you're looking to protect against SQL injection which is something worthwhile doing, consult the following:

You need to declare global scope for those variables inside your function:

function addUser($conn, $firstname, $lastname, $username, $password) {
    global $connection, $iniSalt, $endSalt;
    // Then use those global variables
    ...
}

Document for global keyword here: http://php.net/manual/en/language.variables.scope.php

That's not how globals work. Put global $connection; at the top of your addUser() function to use it in your function.

function addUser($conn, $firstname, $lastname, $username, $password) {
    global $connection;
    ...
}