title: is_file returning false when using absolute path
body: <p>I am trying to use the is_file() function to check if an image exists.
  Here is what I do :</p>
  
  <pre><code>&lt;?php if(is_file("/images/tours/crop/$image")){ ?&gt;
      &lt;img src="/images/tours/crop/&lt;?php echo $image ?&gt;"&gt; 
  &lt;?php } 
  else {echo "Original image has not been cropped yet";} ?&gt;
  </code></pre>
  
  <p>The image exists. When I just output the image, it appears. However, the function always returns false (and I'm getting the error).
  I thought it was a Windows problem, but when putting it on our demo server under Linux, the problem is still here.</p>
  
  <p>Any help appreciated.
  Thanks</p>