title: Why does a backslash in my include_path get mangled?
body: <p>I'm using the following code to be able to easily test my page on my dev machine and the shared host:</p>
  
  <pre><code>$include_path_afrihost = "../php/Services/facebook/php-graph-sdk-5.0.0/src/Facebook";
  $include_path_dev = __DIR__."\sdk\facebook\php-graph-sdk-5.0.0\src\Facebook";
  ini_set("include_path", $include_path_afrihost . PATH_SEPARATOR . $include_path_dev);
  require_once "Facebook.php";
  </code></pre>
  
  <p>When I try and run the code, I get the following exception:</p>
  
  <blockquote>
    <p>require_once(): Failed opening required 'Facebook.php'
    (include_path='../php/Services/facebook/php-graph-sdk-5.0.0/src/Facebook;C:\Dev\PHP\Projects\Messenger\Code\FacebookClient\sdkacebook\php-graph-sdk-5.0.0\src\Facebook')</p>
  </blockquote>
  
  <p>Please note the mess in the dev include path with "\FacebookClient\sdkacebook\", where a backslash and the 'f' for 'facebook' are missing. I copied the path directly from the address bar in Windows File Explorer, and all the other backslashes are fine.</p>
  
  <p>If I change the one line and make the funny backslash double, e.g:</p>
  
  <pre><code>$include_path_dev = __DIR__."\sdk\\facebook\php-graph-sdk-5.0.0\src\Facebook";
  </code></pre>
  
  <p>then the code works fine.</p>