Will reducing number of includes/requires increase performance?

Question

What is better practice for script performance tuning?

This one?

require_once("db.php");

if (!is_cached()) {
  require_once("somefile.php");
  require_once("somefile2.php");
  //do something
} else {
  //display something
}

Or this one?

require_once("db.php");
require_once("somefile.php");
require_once("somefile2.php");

if (!is_cached()) {
  //do something
} else {
  //display something
}

Is it worth placing includes/requires into flow control structures or no?

Thank you

Answer 1

Yes, it will increase performance and contrary to what others said, the impact may not be negligible.

When you include/require files, PHP will check all the defined include_paths until it finds the file or there is nothing more to check. Depending on the amount of include pathes and the amount of files to include, this will have a serious impact on your application, especially when including each and every file up front. Lazy including (like in your first example) or - even better - using the Autoloader is advisable.

Related reading that addresses this in more details:

• Zend Framework Performance Guide*

^{*The advice given there is applicable to any application or framework}