title: file_exists() expects parameter 1 to be a valid path, string given
body: <p>I'm designing a web application that can be customized based on which retail location the end user is coming from. For example, if a user is coming from a store called Farmer's Market, there may be customized content or extra links available to that user, specific to that particular store. file_exists() is used to determine if there are any customized portions of the page that need to be imported.</p>
  
  <p>Up until now, we've been using a relatively insecure method, in which the item ID# and the store are simply passed in as GET parameters, and the system knows to apply them to each of the links within the page. However, we're switching to a reversible hash method, in which the store and item number are encrypted (to look something like "gd651hd8h41dg0h81"), and the pages simply decode them and assign the store and ID variables.</p>
  
  <p>Since then, however, we've been running into an error that Googling extensively hasn't found me an answer for. There are several similar blocks of code, but they all look something like this:</p>
  
  <pre><code>$buttons_first = "../stores/" . $store . "/buttons_first.php";
  
  if(file_exists($buttons_first))
  {
      include($buttons_first);
  }
  </code></pre>
  
  <p>(The /stores/ directory is actually in the directory above the working one, hence the ../)</p>
  
  <p>Fairly straightforward. But despite working fine when a regular ID and store is passed in, using the encrypted ID throws this error for each one of those similar statements:</p>
  
  <blockquote>
    <p>Warning: file_exists() expects parameter 1 to be a valid path, string given in [url removed] on line 11</p>
  </blockquote>
  
  <p>I've had the script spit back the full URL, and it appears to be assigning $store correctly. I'm running PHP 5.4.11 on 1&amp;1 hosting (because I know they have some abnormalities in the way their servers work), if that helps any.</p>