Better PHP Development

Chapter 1: How PHP Executes—from Source Code to Render

by Thomas Punt

Peer reviewed by Younes Rafie.

Introduction

There's a lot going on under the hood when we execute a piece of PHP code. Broadly speaking, the PHP interpreter goes through four stages when executing code:

1. Lexing
2. Parsing
3. Compilation
4. Interpretation

This piece will skim through these stages and show how we can view the output from each stage to really see what is going on. Note that while some of the extensions used should already be a part of your PHP installation (such as tokenizer and OPcache), others will need to be manually installed and enabled (such as php-ast and VLD).

Stage 1 - Lexing

Lexing (or tokenizing) is the process of turning a string (PHP source code, in this ...