Getting Started with PHP Extensions 

Lochemem Bruno Michael ● PHP enthusiast from Kampala, Uganda ● Functional Programming aficionado ● Graduated college in 2019 ● Maintains PHP userland packages and extensions ● Loves ReactPHP ● Authored a book ● Loves hoops, music, movies, podcasts, and video games 

So, PHP extensions? ● Written mainly in C/C++ ● Infuse the PHP userland with ad-hoc functionality ● Require interaction with a low-level PHP engine API 

Why even bother? ● Extensions are typically faster than their PHP equivalents ○ Primarily because they are written in C/C++ ● Extensions allow for infusion of performant ad-hoc solutions ○ Addition of features otherwise not present in PHP userland (ext-uv, ext-apcu) ○ Either unique projects or wrappers around other C/C++ packages ● Extension-building likely results in a better understanding of PHP internals ○ Engaging endeavor likely to test your patience and skill 

Pump the brakes! You have to get familiar with PHP’s lifecycle 

PHP Lifecycle 1. MINIT (Module Initialization) 2. RINIT (Request Initialization) 3. RSHUTDOWN (Request Shutdown) 4. MSHUTDOWN (Module shutdown) MINIT RINIT MSHUTDOWN RSHUTDOWN 

Traditionally... 

Anatomy of an extension ● tests -> *.phpt ○ for module test files ● config.m4/config.w32 ○ for platform-specific configuration options ● ext.cpp|.c/[name].cpp|.c ○ arbitrarily named extension file ● php_ext.h/php_[name].h ○ primary extension header file 

php_trie ● Trie data structures for PHP ● Built in C++ 

So, tries huh? 

What about tries? ● Potent tree structures for storing string data ● Persistent data structures ● Designed for fast traversal and string searches ● Empty root node with multiple child nodes ● Useful as dictionaries and associative maps ● Somewhat space inefficient 

The first thing to do is set things up. 

● Comments ● Configuration option definitions ● Build specifics Configuring the extension (for POSIX systems) 

● Comments ● Configuration option definitions ● Build specifics Configuring the extension (for Windows systems) 

Onto the primary extension header file... 

Salient elements ● Extension info (name, version) ● PHP-engine header file inclusions ● Module definition ● Other discretionary constants 

How about the primary extension file? 

● PHP userland-bound artifacts ● PHP lifecycle handlers php_trie.cpp’s features 

● Extension entry table ● Shared object loading routines php_trie.cpp’s features continued... 

The next thing to do is implement the trie. 

The scope of the implementation ● A single Trie class ● Public constructor ● Two additional methods - insert and search 

● Linked list ● Stores string keys and values ● String values are appendable to the end of each final key node C++ trie object 

● Creates a new trie entry ● Appends string to the end of a branch Insertion 

● Performs trie traversal ● Outputs a matching value at the end of a branch search/lookup 

Onto the PHP engine API side of things... 

What to expect ● Macros, macros, and more macros ● Engine-specific functions ● Memory management ● PHP internals conventions 

● Basis for the PHP userland object ● Contains C++ trie object PHP-C/C++ trie object 

More PHP object-related stuff ● Object handlers ● Class registration ● The MINIT function 

Things to be mindful of when writing functions ● PHP zvals ● Argument parsing ● Return values ● Memory management 

● Zend value container ● PHP variables ● C union ● Has unique macros for multiple use-cases (ZVAL_P, Z_TYPE_P, Z_LVAL_P, etc...) zvals 

● All manner of types (string, float, array, etc...) ● Arguments should be relevant to function Argument parsing 

● PHP engine API return_value variable ● PHP engine API return macros ● Should translate to PHP userland types Return values 

● Allocate something then free it ● Use PHP engine API helpers ● Guards against some nasty leaks and faults Memory management 

● Create a trie ● Initializes the Trie object __construct 

● Takes two arguments ● boolean to zend_bool return value conversion insert 

● Takes one argument ● C++ string to C string conversion search 

How about some tests? 

The .phpt file ● De-facto engine test file format ● Sections vs succinct PHP method assertions (SKIPIF, EXPECT, FILE, etc...) ● Trigger tests by using the directive make test 

All that’s left is to build and use the extension. 

● Requires autoconf, make, gcc, and libtool ● Installs the extension in the PHP modules directory 

Moving Forward... ● Take a look at the Internals book ● Contact someone knowledgeable ● Look at engine code ● Sharpen your C/C++ skills 

Thanks.