controlled 'crements

Have you ever wanted to create a function that would increment an integer position by a certain number as long as it didn't go over a max or under a minimum?

Here's a function I wrote recently that does this:

/**
 * Increment or decrement a given position by a change amount within rules
 *
 * @author Richard AT d2p.us
 * @param int $position
 * @param int $change_by
 * @param int $max
 * @param int $min
 * @param string $incOrDec
 */
function incrementDecrement(&$position, $change_by, $max, $min = 1, $incOrDec = "inc"){
  if ($incOrDec == "inc"){
    if (($position + $change_by ) <= $max){
      $position = $position + $change_by;
    }else {
      $position = $max;
    }
  }else {
    if (($position - $change_by ) >= $min){
      $position = $position - $change_by;
    }else{
      $position = $min;
    }
  }
}

Of course, this doesn't return anything, I have it changing the original position because I pass by reference, but change this to suite you.