Interesting Benchmark on Arrays

I occasionally do some code development for a customer who has a HUGE site (I'd estimate in excess of 500,000 lines of code). I keep running into some really poor coding practices by previous developers. Of course, I get paid for fixing them, so I guess that's good.

One that really drives me up the wall is that there are lots of array references without quote marks on the element names. Because I occasionally have to refer to the error logs to find my coding errors (yes, every once in a while, I make them too), I noticed that the logs filled up fast with messages about the missing quotes and creating new variables. I knew this had to be slowing down the execution.

So I set up a little benchmark on one of my local test sites.

<?php
  $array = array('apple' => 1, 'banana' => 2, 'carrot' => 3, 'date' => 4, 'eggplant' => 5);
  $how_many = 10000;

  $start = microtime(TRUE);

  for ($i = 1; $i <= $how_many; $i++) {
    $a = $array['apple'];
    $b = $array['banana'];
    $c = $array['carrot'];
    $d = $array['date'];
    $e = $array['eggplant'];
  }

  $end = microtime(TRUE);

  $with = $end - $start;
  echo '<p>With quotes took '. number_format($with * 1000000, 2) ." microseconds.</p>";

  $start = microtime(TRUE);

  for ($i = 1; $i <= $how_many; $i++) {
    $a = $array[apple];
    $b = $array[banana];
    $c = $array[carrot];
    $d = $array[date];
    $e = $array[eggplant];
  }

  $end = microtime(TRUE);

  $without = $end - $start;
  echo '<p>Without quotes took '. number_format($without * 1000000, 2) ." microseconds.</p>";
  echo '<p>That\'s '. number_format($without / $with, 1) ." times as long!</p>";
?>

If my benchmark is flawed, I'd love for you to tell me.

Here's the result:

With quotes took 11,510.85 microseconds.

Without quotes took 390,300.99 microseconds.

That's 33.9 times as long!