title: PHP behavior of include/require inside conditional
body: <p>If I place an <code>include</code> or <code>require</code> statement inside a conditional that evaluates to <code>false</code>, will the PHP interpreter skip the include file altogether, or will it load it just in case?</p>
  
  <p>An example would be:</p>
  
  <pre><code>if ($some_user_var) {
      require 'this.php';
  } else {
      //do stuff
  }
  </code></pre>
  
  <p>I read somewhere that <code>require</code> will always be included by the interpreter regardless of the conditional, but <code>include</code> will not. If that's the case, just switching from <code>require</code> to <code>include</code> could mean a free speedup due to the reduced I/O and parsing overhead.</p>
  
  <p>It probably makes a difference if I'm running a preprocessor like eAccelerator, but let's assume I don't.</p>