Drupal l() and url() methods
Both l and url methods are handy to create urls for various entities. However, the variety of options available makes the usage exciting and complex.
l(): Formats an internal or external URL link as an HTML anchor tag.
Syntax: l($text, $path, array $options = array())
Creating an absolute URL using l(). The example below creates a node link.
<?php
l(t('New product'), 'node/123', array('absolute' => TRUE));
?>
Add the previous url or the current page url before going to the new page.