Question

In PHP switch statements, does placing more common cases near the top improve performance?

For example, say the following function is called 1,000 times:

<?php 
function foo_user ($op) {
    switch ($op) {
        case 'after_update':
        //Some Stuff
        case 'login':
        //Some other Stuff
    }
}

If in 990 of the 1,000 of the times the function is called the $op argument is ‘login’, would performance improve by having case: 'login' above case 'after_update': in the switch statement? For example, would the code after case 'after_update': be ignored if $op = login was passed?

I’ve run some informal tests on this idea, but the difference has been negligible — perhaps because the code after case: 'login' and case 'after_update': are both trivial. I’d prefer to avoid setting up a more extensive test with non-trivial operations if someone knows the answer outright.

This is specifically a Drupal question, but I imagine it could be addressed by anyone who is familiar with optimizing PHP.

Answer 1

This is likely going to be called a micro optimisation. I don’t believe there would be a large difference.

However, order does mean a lot to the logic of the switch case if you allow the cases to fall through, example

switch ($var) {

    case 0:
    case 1:
       do_it();
       break;
    case 2:
       do_it_else();
       break;

}

The order is important, the case will fall through and execute any code until it hits a break.

I wouldn’t be concerned about the speed of the switch case, unless you had say 100 possible cases. But if then, it’d be likely you should refactor your code.