PHP has batteries included. For almost everything you can imagine doing, from image manipulation to send e-mail, there is some (poorly conceived) API. And, cou

PHP has batteries included. For almost everything you can imagine doing, from image manipulation to send e-mail, there is some (poorly conceived) API. And, coupled to Apache MPM or equivalent, it offers a very simple model of development with good scalability. A PHP script can work top-to-bottom, as if it were the only thing in the Web server, and MPM will run that script in any number of parallel instances. Many, many developers can't grasp more complex models e.g. Node.js asynchronous. So there is impedance match between some average programmer with a good idea to implement, and the tool. Given these factors, people start some prototype in PHP, and one day the prototype becomes a major product, and rewriting it is prohibitively expensive.