title: Does reading include files slow down php script load?
body: <p>It is very common to use <code>include</code> files. I think it is overused to keep the codes tidy without considering performance. For several <code>include</code>s, disk should read the files, and as we extremely use disk, it can be a slow process. However, this is not the main slow process or the rate-limiting process, as loading the file with <code>file_get_contents</code> is few times faster.</p>
  
  <p>I think this is the reason that major websites put javascripts within the html file rather than loading them by file. Alternatively, it can be a good idea to split a large JS file into several small JS files, as parallel http requests can load the entire JS codes faster. But this is different from php files, as php script reads <code>include</code> files one by one during the process.</p>
  
  <ol>
  <li><p>Please comment how much serious this problem can be? Imagine a webpage is loaded in 0.60s, can <code>include</code> of 10 php files turn it to 0.70s?</p></li>
  <li><p>Although this effect should be negligible, I want to know if there are approaches to speed up this process. I do not mean php caching like <code>APC</code>.</p></li>
  </ol>
  
  <p><strong>P.S.</strong> This question is not for practical application (a typical case), but theoretical considerations in general.</p>