A helpful addition to if statements is the elseif statement, which allows you to chain conditions together in a more intelligent way:
<?php if ($Age < 10) { print "You're under 10"; } elseif ($Age < 20) { print "You're under 20"; } elseif ($Age < 30) { print "You're under 30"; } elseif ($Age < 40) { print "You're under 40"; } else { print "You're over 40"; } ?>