May, 2008

An absolute URL is complete and ready to use to download a web file. But web pages often include incomplete relative URLs with missing parts, such as an "http" or host name, or the first part of a file path. These parts need to be filled in by copying them from a base absolute URL. This article shows how and includes code to do it.

Splitting apart and rebuilding URLs is essential for link checkers, phishing detectors, spiders, and so on. PHP's standard parse_url( ) function works pretty well to parse simple URLs, but it has problems with complex and relative URLs. Once split apart, there is no standard PHP function to reassemble the URL properly. This article reviews the official syntax of URLs, discusses URL parsing complexities, and provides new PHP functions to split apart a URL and join its parts together again.