PHP build system

This repository delves into the core of the PHP build system, elucidating the intricacies of how to build PHP with CMake.

Quick usage - TL;DR

Step 1 - Install prerequisites

# Prerequisites for Debian-based distributions:
sudo apt install cmake gcc g++ bison libxml2-dev libsqlite3-dev

# Prerequisites for Fedora-based distributions:
sudo dnf install cmake gcc gcc-c++ bison libxml2-devel sqlite-devel

Click here for more platforms

# Prerequisites for macOS:
xcode-select --install   # XCode command line tools
brew install cmake bison # See https://brew.sh how to install Homebrew

# Prerequisites for Alpine Linux:
sudo apk add --no-cache cmake make gcc g++ bison libxml2-dev sqlite-dev

# Prerequisites for BSD-based systems:
sudo pkg install cmake bison libxml2 sqlite3

# Prerequisites for Haiku:
pkgman install cmake bison libxml2_devel sqlite_devel

# Prerequisites for Solaris/illumos-based systems:
sudo pkg install cmake bison libxml2 sqlite-3

Step 2 - Clone this repository

git clone https://github.com/petk/php-build-system

cd php-build-system

Step 3 - Download PHP and add CMake files

cmake -P bin/php.cmake

Step 4 - Generate build system to a build directory

cmake -S php-8.4-dev -B php-build

Step 5 - Build PHP in parallel

cmake --build php-build -j

After build is complete, you should have a PHP binary that can be run on the command line:

./php-build/sapi/cli/php -v

Introduction

PHP developers typically opt for convenient methods to set up PHP on their machines, such as utilizing prebuilt Linux packages available in their Linux distribution repositories, deploying Docker images, or relying on user-friendly stacks that bundle PHP, its extensions, web server, and database into a unified installation package.

# Debian-based distributions:
sudo apt install php...

# Fedora-based distributions:
sudo dnf install php...

In contrast, the practice of building PHP from source code is primarily reserved for specific purposes, such as PHP source code development or extensive customization of PHP configurations on a particular system. This approach is less commonly employed by everyday PHP developers due to its intricate and time-consuming nature.

In the realm of software development, a build system is a collection of tools and files that automate the process of compiling, linking, and assembling the project's source code into its final form, ready to be executed. It helps developers with repetitive tasks and ensures consistency and correctness in the build process for various platforms and hardware out there.

A key function of a build system in the context of C/C++ software development is to establish a structured framework that guides how code should be written. Beyond its primary role of compiling source files into executable programs, the build system plays a pivotal educational role, imparting best practices and coding standards to developers. By enforcing consistency and adherence to coding conventions, it fosters the creation of high-quality code, ultimately enhancing software maintainability and reliability.

Additionally, the build system aims to enable developers to work efficiently by abstracting away system-specific details, allowing them to focus on the logic and usability of their code. When adding a new source file or making minor modifications, developers shouldn't have to delve into the inner workings of the build system, sift through extensive build system documentation or extensively explore the complexities of the underlying system.

There are numerous well-known build systems available, ranging from the veteran GNU Autotools and the widely adopted CMake, to the efficient Ninja, versatile SCons, adaptable Meson, nimble xmake, and even the simplest manual usage of Make.

PHP directory structure

To understand the PHP source code better, it would be beneficial to grasp its directory structure. PHP is developed at the php-src GitHub repository.

After cloning the repository:

git clone https://github.com/php/php-src
cd php-src

you end up with a large monolithic repository consisting of C source code files, PHP tests and other associated files:

<php-src>/
 ├─ .git/                         # Git configuration and source directory
 ├─ benchmark/                    # Benchmark some common applications in CI
 ├─ build/                        # *nix build system files
 ├─ docs/                         # PHP internals documentation
 └─ ext/                          # PHP core extensions
    └─ bcmath/                    # The bcmath PHP extension
       ├─ libbcmath/              # The bcmath library forked and maintained in php-src
       ├─ tests/                  # *.phpt test files for extension
       ├─ bcmath.stub.php         # A stub file for the bcmath extension functions
       └─ ...
    └─ curl/                      # The curl PHP extension
       ├─ sync-constants.php      # The curl symbols checker
       └─ ...
    └─ date/                      # The date/time PHP extension
       └─ lib/                    # Bundled datetime library https://github.com/derickr/timelib
          └─ ...
       └─ ...
    ├─ dl_test/                   # Extension for testing dl()
    └─ dom/
       ├─ lexbor/                 # https://github.com/lexbor/lexbor
       └─ ...
    └─ ffi/                       # The FFI PHP extension
       ├─ ffi_parser.c            # Generated by https://github.com/dstogov/llk
       └─ ...
    └─ fileinfo/                  # The fileinfo PHP extension
       ├─ libmagic/               # Modified libmagic https://github.com/file/file
       ├─ data_file.c             # Generated by `ext/fileinfo/create_data_file.php`
       ├─ libmagic.patch          # Modifications patch from upstream libmagic
       ├─ magicdata.patch         # Modifications patch from upstream libmagic
       └─ ...
    └─ gd/                        # The GD PHP extension
       ├─ libgd/                  # Bundled and modified GD library https://github.com/libgd/libgd
       └─ ...
    └─ mbstring/                  # The Multibyte string PHP extension
       ├─ libmbfl/                # Forked and maintained in php-src
       ├─ unicode_data.h          # Generated by `ext/mbstring/ucgendat/ucgendat.php`
       └─ ...
    └─ opcache/                   # The OPcache PHP extension
       └─ jit/                    # OPcache Jit
          └─ ir/                  # Bundled part of IR framework https://github.com/dstogov/ir
             └─ dynasm/           # DynASM encoding engine
                ├─ minilua.c      # Customized Lua scripting language to build LuaJIT
                └─ ...
             ├─ gen_ir_fold_hash  # IR folding engine generator created at build
             ├─ ir_emit_<arch>.h  # IR folding engine rules generated by minilua
             ├─ minilua           # Executable tool created at build
             └─ ...
    └─ pcre/                      # The PCRE PHP extension
       ├─ pcre2lib/               # https://www.pcre.org/
       └─ ...
    ├─ skeleton/                  # Skeleton for new extensions using `ext/ext_skel.php`
    └─ standard/                  # Always enabled core extension
       └─ html_tables/
          ├─ mappings/            # https://www.unicode.org/Public/MAPPINGS/
          └─ ...
       ├─ credits_ext.h           # Generated by `scripts/dev/credits`
       ├─ credits_sapi.h          # Generated by `scripts/dev/credits`
       ├─ html_tables.h           # Generated by `ext/standard/html_tables/html_table_gen.php`
       └─ ...
    └─ tokenizer/                 # The tokenizer PHP extension
       ├─ tokenizer_data.c        # Generated by `ext/tokenizer/tokenizer_data_gen.php`
       ├─ tokenizer_data_stub.php # Generated by `ext/tokenizer/tokenizer_data_gen.php`
       └─ ...
    └─ zend_test                  # For testing internal APIs. Not needed for regular builds
       └─ ...
    └─ zip/                       # Bundled https://github.com/pierrejoye/php_zip
       └─ ...
    ├─ ...
    └─ ext_skel.php               # Helper script that creates a new PHP extension
 └─ main/                         # Binding that ties extensions, SAPIs, Zend engine and TSRM together
    ├─ streams/                   # Streams layer subsystem
    └─ ...
 ├─ modules/                      # Shared libraries, created when building PHP
 ├─ pear/                         # PEAR installation
 └─ sapi/                         # PHP SAPI (Server API) modules
    └─ cli/                       # Command-line PHP SAPI module
       ├─ mime_type_map.h         # Generated by `sapi/cli/generate_mime_type_map.php`
       └─ ...
    └─ ...
 ├─ scripts/                      # php-config, phpize and internal development scripts
 ├─ tests/                        # Core features tests
 ├─ travis/                       # Travis CI service files
 ├─ TSRM/                         # Thread safe resource manager
 └─ Zend/                         # Zend engine
    ├─ asm/                       # Bundled from src/asm in https://github.com/boostorg/context
    ├─ Optimizer/                 # For faster PHP execution through opcode caching and optimization
    ├─ tests/                     # PHP tests *.phpt files for Zend engine
    ├─ zend_vm_execute.h          # Generated by `Zend/zend_vm_gen.php`
    ├─ zend_vm_opcodes.c          # Generated by `Zend/zend_vm_gen.php`
    ├─ zend_vm_opcodes.h          # Generated by `Zend/zend_vm_gen.php`
    └─ ...
 ├─ win32/                        # Windows build files
 └─ ...

Why CMake?

At the time of writing, CMake is actively developed, and many developers may already be familiar with it, making C code more appealing to new contributors. Numerous IDEs offer excellent CMake integration for C/C++ projects.

CMake shares many similarities with Autotools, which simplifies the learning curve for those already accustomed to building C code using existing systems.

Notably, CMake features better out-of-the-box support on Windows systems, where Autotools may encounter issues without additional adaptations and adjustments in the build process.

Despite Autotools potentially seeming complex and arcane to new developers, unfamiliar with it, it remains a robust and solid build system option for C/C++ projects on *nix systems. Many large open-source projects use Autotools, and some even incorporate it alongside CMake.

oplanre/build-php