How to cap a PHP int value

You could use min:

min($sum, 100)

This returns either $sum if $sum < 100 or 100 otherwise.

You can just use the min function:

$result = min($result, 100);

You'd have to check them I guess.

$x    = 80;
$y    = 50;
$z    = $x + $y;
$int  = ($z > 100) ? 100 : $z;