Insert into MySQL database via PHP only half working - php

Question

So I'm currently learning PHP, and I'm creating a simple PHP page with a signup form using the POST method. On form submit, the page hashes the password (with phpass), verifies the username is valid (that is, it doesn't exist currently in the db) and inserts if that's true. My code is inserting new rows, but I'm not seeing values for username or hash values being stored. Here's the PHP:
require("PasswordHash.php");
$unSuccess = false;
$pwSuccess = false;
$registerSuccess = false;
$spamSuccess = false;
$database = "XXXXXXX";
$username = "XXXXXXX";
$password = "XXXXXXX";
$server = "XXXXXXX";
$db = new mysqli($server, $username, $password, $database);
$user = "";
$pass = "";
if (mysqli_connect_errno())
{
printf("Connection failed: %s\n", mysqli_connect_error());
exit();
}
if($_POST["usr"] && !$unSuccess){
$un = $_POST["usr"];
if(strlen($un) < 20){
//Verify Username is valid
if(preg_match("/([A-Za-z0-9])/", $un) == 1){
//Username is valid, check if it already exists in db.
$unCheckQuery = "SELECT USERS.Username FROM USERS WHERE USERS.Username = '$un'";
$result = $db->query($unCheckQuery);
$num = $result->num_rows;
$result->close();
if($num != 0){ $errUsername = "Username already exists."; $unSuccess = false; }
}
else{
//Username is valid and not taken
$user = $un;
$unSuccess = true;
}
}
}
if($_POST["password"] && !$pwSuccess){
//verify and hash pw
$pw = $_POST["password"];
if(str_len($pw) > 72){die("Password must be shorter than 72 characters");}
$hasher = new PasswordHash(8, false);
$hash = $hasher->HashPassword($pw);
if(strlen($hash) >= 20 && preg_match($pattern, $pw) == 1){
$pass = $hash;
echo $pass;
$pwSuccess = true;
}
else{
$pwSuccess = false;
}
}
if($_POST["spam"]){
$s = $_POST["spam"];
if($s != 10){
$spamSuccess = false;
}
else if($s == 10) {$spamSuccess = true;}
}
if($unSuccess = true && $pwSuccess = true && $spamSuccess = true){
$registerQuery = "INSERT INTO USERS(Username, phash) VALUES('$user', '$pass')";
//This line is breaking evrything.
$db->query($registerQuery);
}
The form I'm using is a simple HTML form. I have omitted login information for obvious reasons. Any pointers in the right direction would be greatly appreciated!

Answer 1

if($unSuccess = true && $pwSuccess = true && $spamSuccess = true)
needs to be
if($unSuccess == true && $pwSuccess == true && $spamSuccess == true)

Answer 2

Turns out this particular issue was being caused by a security issue on the server end. This code is syntactically correct.