title: Why is PHP not including my file when it clearly exists?
body: <p>Here is the exact problem.  I have an autoload function set up with a piece of code that looks like this:</p>
  
  <pre><code>if(file_exists($class_file))
  {
      include($class_file);
      return true;
  }
  </code></pre>
  
  <p>However, when <code>$class_file</code> is set to a certain value, I get an include error: </p>
  
  <pre><code>Error String: include(includes/php/utilities/calendar_event_html.utility.php)
  [function.include]: failed to open stream: No such file or directory
  </code></pre>
  
  <p>It works fine for other files and when I step through this code with a debugger it is clear that PHP believes the file exists, but it seems that <code>include</code> does not.  Does anyone have an idea of what is going on?</p>