[UPHPU] require_once vs. class_exists

[Alvaro Carrasco]

Rusty Keele wrote:
> Hi,
>
>   Which is a better approach to use:
>   
>   1. require_once('path/to/class.php');
>
>   or
>
>   2. if(!class_exists('path/to/class.php')) require('path/to/class.php');
>
>   I have been using the first approach in all my files where I need to instantiate a specific class, but I am wondering if the second approach is more efficient?  Are there any benefits to using the second approach - such as less caching of objects - or do these two statements do the same thing?
>
> Thanks,
> Rusty
>
>
>
>   

Keep in mind that f you are using a byte-code cache such a APC or 
eAccelerator (you're using one, right :) ), it probably won't be able to 
cache the code for classes that are included conditionally.
So, the performance when using a byte-code cache generally goes 
something like this:

require                                           best
require_once                                  ok
autoload or conditional include        bad

Alvaro