simple function to relativize request to a WP site

relativize_path.php

<?php

/**
* Return the request path, relative to the WP base URL
* @param boolean $return_parts Return as a string or an array
* @return string|array The relative request OR array with relative "directories"
*/
function relativize_url($return_parts=true){
	$wp_url = get_bloginfo('url'); //base URL for this WordPress site
	$wp_url_parts = parse_url($wp_url); //
	$protocol = ( $_SERVER['HTTPS'] ) ? 'https://' : 'http://';
	$full_url = $protocol . $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI']; // the complete URL for this request
	$url_parts = parse_url($full_url);
	$request_path = str_replace($wp_url_parts['path'], '', $url_parts['path']); // request path, relative to the WP install
	if ( $return_parts) return array_values(array_filter(explode('/', $request_path))); // decomposed relative request path
	else return $request_path;
}

?>