When the execution is not explicitly terminated at the end of a switch case, it continues to execute the statements of the following case. While this is sometimes intentional, it often is a mistake which leads to unexpected behavior.

Noncompliant Code Example

switch ($myVariable) {
  case 1:
    foo();
    break;
  case 2:  // Both 'doSomething()' and 'doSomethingElse()' will be executed. Is it on purpose ?
    do_something();
  default:
    do_something_else();
   break;
}

Compliant Solution

switch ($myVariable) {
  case 1:
    foo();
    break;
  case 2:
    do_something();
    break;
  default:
    do_something_else();
   break;
}

Exceptions

This rule is relaxed in following cases:

switch ($myVariable) {
  case 0:                  // Empty case used to specify the same behavior for a group of cases.
  case 1:
    do_something();
    break;
  case 2:                  // Use of continue statement
    continue;
  case 3:                  // Case includes a jump statement (exit, return, break &etc)
    exit(0);
  case 4:
    echo 'Second case, which falls through';
    // no break        <- comment is used when fall-through is intentional in a non-empty case body
  default:                 // For the last case, use of break statement is optional
    doSomethingElse();
}

See