"PHP Web applications are a cinch to start. The syntax of the
PHP language is uncluttered and easy to master. You can mix PHP
quickly. And PHP applications are a snap to deploy on your own Web
server or on a hosting service.
"But the ease of mixing PHP and other page markup is also a
liability. PHP code is often a tangled web (no pun intended) of
program logic, Structured Query Language (SQL) queries, functions,
classes, developer comments, HTML, CSS styles, and scripts..."