Help Cleanup code please?

The code below is not working properly and a little help from the DP community cleaning it up and explaining why you would change certain areas would help me greatly.

Thank you in advance

function treasury() { // Treasury Info.
    
    global $userrow, $numqueries;

    $bankquery = doquery("SELECT username FROM sw_users WHERE id='".$userrow["id"]."' LIMIT 1", "users");
    if (mysql_num_rows($bankquery) != 1) { display("Cheat attempt detected.<br /><br />Your username has been logged ... consider this a warning.", "Error"); }
    $bankrow = mysql_fetch_array($bankquery);
    
    
    if (isset($_POST["submit"])) {
        
        $newgold = $userrow["gold"] - $userrow["gold"];
        $query = doquery("UPDATE sw_users SET gold='$newgold',bank='".$userrow["bank"] + '$newgold'."' WHERE id='".$userrow["id"]."' LIMIT 1", "users");
        $title = "Treasury";
        $page = "You leave the Treasury feeling safe that Your hard earned gold is protected.<br /><br />You may return to <a href=\"index.php\">town</a>, or use the direction buttons on the left to start exploring.";
        
    } elseif (isset($_POST["cancel"])) {
        
        header("Location: index.php"); die();
         
    } else {
        
        $title = "Treasury";
        $page = "Placing gold in the treasury will keep it safe from Monsters and other Players.<br />You currently must deposit all Gold.<br /><br />\n";
        $page .= "You Currently have <b>". $bankrow['bank'] ." gold</b> in the Treasury at this time.<br /><br />\n";
        $page .= "<form action=\"index.php?do=treasury\" method=\"post\">\n";
        $page .= "<input type=\"submit\" name=\"submit\" value=\"Yes\" /> <input type=\"submit\" name=\"cancel\" value=\"No\" />\n";
        $page .= "</form>\n";
        
    }
    
    display($page, $title);

}

Code (markup):

I am new at functions so any input would help me greatly

 

Okay I will be more specific where my initial problem is here is the code followed by the problem:

global $userrow, $numqueries;

    $bankquery = doquery("SELECT username FROM sw_users WHERE id='".$userrow["id"]."' LIMIT 1", "users");
    if (mysql_num_rows($bankquery) != 1) { display("Cheat attempt detected.<br /><br />Your username has been logged ... consider this a warning.", "Error"); }
    $bankrow = mysql_fetch_array($bankquery);

$page .= "You Currently have <b>". $bankrow["bank"] ." gold</b> in the Treasury at this time.<br /><br />\n";

Code (markup):

". $bankrow["bank"] ." <---Displays nothing not even a 0 or error?

 

$bankquery = doquery("SELECT username FROM sw_users WHERE id='".$userrow["id"]."' LIMIT 1", "users");

You are only requesting the username from the database.