Zend Server is described as 'is the #1 professional PHP stack. It is the most complete PHP distribution with a continuously updated set of advanced value-add features designed to optimize productivity, performance, scalability and reliability' and is an app in the Development category. There are more than 10 alternatives to Zend Server for a variety of platforms, including Windows, Mac, Linux, Online / Web-based and Self-Hosted solutions. The best alternative is XAMPP, which is both free and Open Source. Other great apps like Zend Server are MAMP (Freemium), AMPPS (Free), Fenix Web Server (Free, Open Source) and Open Server (Free).
XAMPP is a completely free, easy to install Apache distribution containing MariaDB, PHP, and Perl. The XAMPP open source package has been set up to be incredibly easy to install and to use. XAMPP is free even for commercial uses
MAMP installs a local server environment in a matter of seconds on your computer. It comes free of charge, and is easily installed. MAMP will not compromise any existing Apache installation already running on your system.
Open Server - a portable server platform and software environment designed specifically for web developers, taking into account their recommendations and suggestions. Open Server is much more functional than complex software like XAMPP or WAMPSERVER.