Here’s a fun little trick. When looping over an array, you can access the values by reference. Instead of:

foreach ($things as $i => $thing)
{
  $things[$i] = strtolower($thing);
}

You can reference the values of the array:

foreach ($things as &$thing)
{
  $thing = strtolower($thing);
}

It’s a small difference, but it comes in handy once in a while, especially when you’re doing more significant processing with each item.