Untitled

How do I make include use local directories in php
<?php
$path_of_this_script = dirname(__FILE__);
[...]

<?php
function include_image() {
  $image_url = "icon.png"; // Will search for icon.png in "files" directory
  //do something with $image_url
}
?>

<?php
$image_path = "http://www.example.com/images"; // or "foldername/subfoldername/images"
?>

<?php
include "vars.php";
function include_image() {
  $image_url = "$image_path/icon.png"; // Will search for icon.png in "files" directory
  //do something with $image_url
}
?>