Takes input from a file or stream containing text and PHP instructions
Outputs stream of data for display
PHP originally interpreted, not converted to binary executable files
PHP 4 – parser compiles input to produce bytecode (semi-compiled) – Zend engine (better performance than interpreted PHP 3)
PHP 5 – robust support for OO programming, better support for MySQL, support for SQLite, performance enhancements
SQLite – ACID compliant embedded relational DB contained in small C programming library. Source code in public domain. SQLite library is linked in and part of application program, uses simple function calls, reducing latency. Entire DB stored as a single file on a host machine.