What is the benefit of zend server over plain Apache?

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http://serverfault.com – What are the clear benefits of using Zend Server PHP stack against an *AMP(for example LAMP) stack? Or Vice versa? What are the benefits of using a *AMP(for example LAMP) over zend server? Additional information: I recently Acquired my own VPS(which has ubuntu 12.04.2 preinstalled), which allows me to build my own web server from the ground up. So far i used LAMP which usually was my development environment so i didn't really need, any advanced futures, but i never built an actual professional server. Is it worth using zend server for a production server, or LAMP with more customization is (HowTos)