Some PHP performance tips

I sometimes run some «scientific» (read «completely biased») benchmarking for my PHP code to check for the most optimized way of writing some expression. But I keep on forgetting. So this is the place where I'm going to keep some references.

So, to keep thing short, I'm just going to make some bold assertions here (sue me).

Boolean casting

Sometimes you just need to check if a string is «true» or not. Usually I use empty() to avoid Notices, but sometimes I like it quick and dirty. So, in that case:

$string = 'my string';

// This is slower
if ((bool) $string) {
  // Do stuff
}

// This is faster
if (!!$string) {
  // Do stuff
}

Notice the double negate sign to get «true» instead of «false». This trick is also very handy when you really need a boolean and not null or undefined.

And by the way, empty() is slower in this particluar use-case.

Set a flag in a loop

Ever used the trusty $first boolean flag in a loop ? Ever wondered which was faster: just setting it to false at the end of each loop, or checking if it's true and setting it only once ? Well, not that surprizingly, it's the second one (but by a tiny margin).

$first = TRUE;

// This is slower
while(...) {
  // Do stuff

  $first = FALSE;
}

// This is faster
while(...) {
  // Do stuff

  if ($first) {
    $first = FALSE;
  }
}

Check if an array is empty

When you want to check if an array is empty, turns out there's a really fast way to get this info: empty().

$items = array();

// This is slowest
if (count($items) == 0) {
  // Do stuff
}

// This is slower (but faster than the previous)
if (!count($items)) {
  // Do stuff
}

// This is 2x faster
if (empty($items)) {
  // Do stuff
}