If the same logic is truly needed for both instances, then:

* in an `if` chain they should be combined

[source,php,diff-id=1,diff-type=compliant]
----
if (($a >= 0 && $a < 10) || ($a >= 20 && $a < 50)) {
  doFirst();
  doTheThing();
}
else if ($a >= 10 && $a < 20) {
  doTheOtherThing();
}
----

* for a `switch`, one should fall through to the other

[source,php,diff-id=2,diff-type=compliant]
----
switch ($i) {
  case 1:
  case 3:
    doFirst();
    doSomething();
    break;
  case 2: 
    doSomethingDifferent();
    break;
  default: 
    doTheRest();
}
----