Convert a relative URL to absolute one, depends on the current base URL.

convertRelativeToAbsolute.php

<?php

function convertRelativeToAbsolute($relativeUrl, $baseUrl)
{
	preg_match('/^([\w\d]+?):\/\/([^\/]+)(\/[^\?#\.]+)?/', $baseUrl, $match);

	$scheme = $match[1];
	$host = $match[2];

	$basePath = '/';
	if(!empty($match[3]))
	{
		$basePath = $match[3];
	}

	$baseDir = substr($basePath, 0, strrpos($basePath, '/'));
	
	if(strpos($relativeUrl, '?') !== false)
	{
		list($relativeUrl, $queryString) = explode('?', $relativeUrl);
	}

	$currentDirArr = explode('/', $baseDir);
	$relativeUrlArr = explode('/', $relativeUrl);

	foreach($relativeUrlArr as $dir)
	{
		if($dir == '..')
		{
			array_pop($currentDirArr);
		}
		else if($dir != '.')
		{
			$currentDirArr[] = $dir;
		}
	}
	
	$absUrl = "$scheme://$host" . '/' . ltrim(implode('/', $currentDirArr), '/');
	if(!empty($queryString))
	{
		$absUrl .= "?$queryString";
	}
	return $absUrl;
}