Disadvantage of using filters & hooks multiple times

Question

I'm planning on enforcing a rule in my project to write the codes for a single filter or hook in a single function for easier code maintenance, so instead of having

add_filter('wp','function_a');
function_a() {
    //code A goes here
}

add_filter('wp','function_b');
function_b() {
    //code B goes here
}

It will be reduced to:

add_filter('wp','function_ab');
function_ab() {
    //code A goes here
    //code B goes here
}

My question is, is there also a significant performance benefit by doing this?

Answer 1

Creating a program should be a balanced on how the efficiency of the code work and how easy for future maintenance.

For programming efficiency, both style 1 and style 2 of your code is not make a huge impact much. Because of in nowaday PHP, it converts the code into the bytecode only one time, and read it when visitor using it. So the performance is almost the same.

For future maintenance, it's depend on your team style of coding. Pick one that you more understand on it. For me, the first style is more practical because 1 function do only 1 job and it's much easier for maintenance. That's is.

Answer 2

Adding callbacks is basically free. Add this to your functions.php or create a new plugin for it.

timer_start();
$test = new test();
add_filter( 'all', [ $test, 'all' ] );
add_action( 'shutdown', [ $test, 'shutdown' ] );
class test {
  protected $num = 0;
  function all( $var ) {
    $this->num = $this->num + 1;
    return $var;
  }
  function shutdown() {
    var_dump( $this->num );
    var_dump( timer_stop() );
  }
}

Notice the number of callbacks (the first number var_dumped). It will probably be in the hundreds or thousands. Now remove the all filter. The second number dumped will decrease, and by a noticeable number, but still remarkably small.

When I tried this on my box, I had around 3000 callbacks that fired. When then all filter was added, it took around 0.02s to render and when it wasn't added, it took about 0.01s to render. So adding 3000 callbacks made the page render 0.01s slower. If you're Google, that makes a huge difference. But you're not, so it doesn't.