Add to Value Up to Certain Point

[Octet]

I am creating my purchasing system for my game at the moment, but I am struggling on a part of it and wondered if any of you could offer me some guidance?

The problem I am facing is adding X amount onto a value but if that means it goes over Y then only add up to Y. The player shall purchase a piece of food that shall raise their health by 20 (with 100 being full health), how do I make it so that if the current health value is 90 then it won't go to 110 e.t.c.

So far I have:

<?php

    session_start();

    mysql_connect ("localhost", "root", "") or die ("Couldn't Connect to Server");
    mysql_select_db ("Database") or die ("Couldn't Find Database");

    $Purchase = mysql_real_escape_string($_POST['Purchase']);
    $Username = $_SESSION['Username'];

    $Money = mysql_query ("SELECT * FROM Character_Data WHERE Username = $Username");
    while ($Results = mysql_fetch_array($Money))
    {

        /* Purchase of Meals */

        if($Purchase = "Peasant")
        {
            if($Results['Silver'] >= 20)
            {
                $Withdraw = $Results['Silver'];
                $Withdraw = $Withdraw - '20';

                $Stamina = $Results['Stamina'];

                /* HELP - ADD TO STAMINA BUT NO FURTHER THAN 100 */

                $Health = $Results['Health'];

                /* HELP - ADD TO HEALTH BUT NO FURTHER THAN 100 */

                mysql_query ("UPDATE Character_Data SET Silver = $Withdraw WHERE Username =$Username");
            }

            die (Header ('Location: ../Errors/Money.php'));
        }

    }

?>

I hope you understand and that you shall be able to understand me. I don't want the player to be able to gain more than 100% health or stamina through eating.

(I haven't tested the above code so it might spit out some errors)

Thank you

[blocblue]

You could add something simple like this following after increasing the health value.

$health = min($health, 100);