PHP, included more than one time require include_once or include?
<p>I'am asking myself why should i use include or include_once.</p>

<p>I know there is a question <a href="http://stackoverflow.com/questions/186338/why-is-require-once-so-bad-to-use">about it</a>, but i dont find my answer in it.</p>

<p>In my case my problem is a little bit different, but it can summarize as following.
If i use 4 files who includes themselves, by example:</p>

<p>A includes D</p>

<p>B includes C,D</p>

<p>C no include</p>

<p>D includes C</p>

<p>Should i use "include" or "include_once", and why ?</p>

<p><strong>EDIT</strong></p>

<p>Little mistake in the problem. I just rewrite.</p>

<p><strong>EDIT</strong></p>

<p>To explain my self, D need C to works, but C does not need for D to works. Sometime i have to include C, sometimes i have to include D. D has been refactored, so now it includes C automatically, but there is more than 2 thousand files to review in many directories... so i'am wondering if i use a "include_once" in D is better to use a "include" in D.</p>
