title: is_file or file_exists in PHP
body: <p>I need to check if a file is on HDD at a specified location ($path.$file_name).   </p>
  
  <p>Which is the difference between <a href="http://www.php.net/manual/en/function.is-file.php" rel="noreferrer"><code>is_file()</code></a> and <a href="http://www.php.net/manual/en/function.file-exists.php" rel="noreferrer"><code>file_exists()</code></a> functions and which is better/faster to use in PHP?</p>