Fix a simple PHP script

I wrote a script to open, edit and save a css file. It only works if I put the css file in the same directory as the php script. I need it to work when the css file is in a different directory to the css script. For example: The script is located in: /public_html/admin/[login to view URL] The file I want to edit is located in: /public_html/includes/templates/responsive_classic/css/[login to view URL] Please look at the script and see what is wrong. The code I am using is: <?php if($_POST['Submit']){ $open = fopen('../includes/templates/responsive_classic/css/[login to view URL]',"w+"); $text = $_POST['update']; fwrite($open, $text); fclose($open); echo "File updated.<br />"; echo "File:<br />"; $file = file('../includes/templates/responsive_classic/css/[login to view URL]'); foreach($file as $text) { echo $text."<br />"; } }else{ $file = file('../includes/templates/responsive_classic/css/[login to view URL]'); echo "<form action=\"".$PHP_SELF."\" method=\"post\">"; echo "<textarea Name=\"update\" cols=\"35\" rows=\"35\">"; foreach($file as $text) { echo $text; } echo "</textarea>"; echo "<input name=\"Submit\" type=\"submit\" value=\"Update\" />\n </form>"; } ?>