title: unlink() Function invalid argument
body: <p>I have a file with directory: <code>PDF\9783790820874-c1.pdf</code><br>
  I would like to delete this file with <code>unlink()</code> funciton. But it seems like not working if I set the directory into a variable and unlink it.<br>
  For example: </p>
  
  <pre><code>$FileToDelete = "PDF\9783790820874-c1.pdf";
  unlink($FileToDelete);
  </code></pre>
  
  <p>The code is logic isn't it? but why when I execute it, it show me error message: <br></p>
  
  <pre><code>Warning: unlink(PDF\9783790820874-c1.pdf ): Invalid argument on line 36
  </code></pre>
  
  <p>I have to save file directory into a variable to work well with my program, is there any way to solve it?</p>