After having revolutionised PHP by creating PHP 3, both Andi Gutmans and Zeev Suraski went on to design and create PHP 4, another revolution for the language - no longer would each line of code need to be interpreted as it was read, because Andi and Zeev made the language compiled.
They did this by creating a new engine for the language, known as the Zend Engine - as well as making scripts compiled, the Zend Engine also offered much more flexibility to the programmers of PHP itself, making it easy to port across platforms and servers. The Zend Engine was the first product to come out from Zend, a company founded by Andi and Zeev to create commercial products for PHP. The Zend Engine itself, being an integral part of PHP, is completely free and always will be, however Zend also produce a variety of other products for PHP, including a development environment, a script encoder, and more.
Having two out of the three language architects working for them gives Zend a big advantage in the market place, and as such they produce some excellent products. We will be covering some of their products, as well as their competitors, later in the book.