PHP mySQL Update Query

I have this code:

			$Spy = mysql_real_escape_string($_POST['Spy']);
			$Guard = mysql_real_escape_string($_POST['Guards']);
			$Swordsmen = mysql_real_escape_string($_POST['Swordsmen']);
			$Spearmen = mysql_real_escape_string($_POST['Spearmen']);
			$Archer = mysql_real_escape_string($_POST['Archer']);
			$Macemen = mysql_real_escape_string($_POST['Macemen']);
			$grab_unit_cost = mysql_query("SELECT Unit_Cost FROM " .$_SESSION['Server']. "_Units") or die(mysql_error());
			while($row = mysql_fetch_array($grab_unit_cost))
			{
				$Unit_Cost += $row['Unit_Cost'];
			}
			$Buy_Units = "UPDATE " .$_SESSION['Server']. "_kingdoms SET Spy = Spy + $Spy, Guard = Guard + $Guard, Swordsmen = Swordsmen + $Swordsmen, Spearmen = Spearmen + $Spearmen, Archer = Archer + $Archer, Macemen = Macemen + $Macemen, Kingdom_Gold = Kingdom_Gold - $Unit_Cost";
			mysql_query($Buy_Units) or die(mysql_error());
			echo 'Units successfully bought, <a href="game.php?act=Training">continue training</a>.';

Code (markup):

It gives me this error:

Any idea what I am doing wrong? Well, I know what I am doing wrong but not sure how to do it right.

Thanks,
-Ryu

 

try this query

$Buy_Units = "UPDATE " .$_SESSION['Server']. "_kingdoms SET Spy = Spy + '" .$Spy. "', Guard = Guard + '" .$Guard. "', Swordsmen = Swordsmen + '" .$Swordsmen. "', Spearmen = Spearmen + '" .$Spearmen. "', Archer = Archer + '" .$Archer. "', Macemen = Macemen + '" .$Macemen. "', Kingdom_Gold = Kingdom_Gold - '" .$Unit_Cost. "'";

Code (markup):

 

You can simply add intval in each mysql_real_escape_string line. Example:

$Spy = intval(mysql_real_escape_string($_POST['Spy']));

The issue is that the script handles the variables you want to add to the database as text not integer. So, when they are empty, their value is "" instead of 0. By adding intval, you force it to make them 0 if they are empty.