PHPCrawl is a framework for crawling/spidering websites written in the programming language PHP, so just call it a webcrawler-library or crawler-engine for PHP
PHPCrawl "spiders" websites and passes information about all found documents (pages, links, files ans so on) for futher processing to users of the library.
It provides several options to specify the behaviour of the crawler like URL- and Content-Type-filters, cookie-handling, robots.txt-handling, limiting options, multiprocessing and much more.
PHPCrawl is completly free opensource software and is licensed under the GNU GENERAL PUBLIC LICENSE v2.
To get a first impression on how to use the crawler you may want to take a look at the quickstart guide or an example inside the manual section.
A complete reference and documentation of all available options and methods of the framework can be found in the classreferences-section
The current version of the phpcrawl-package and older releases can be downloaded from a sourceforge-mirror.
Note to users of phpcrawl version 0.7x or before: Although in version 0.8 some method-names and parameters have changed, it should be fully compatible to older versions of phpcrawl.