PHP Source Code (php-src)

The libsodium PHP extension provides a simple, low-level interface to the libsodium cryptographic library. It is designed for modern, secure, and fast cryptography within PHP applications.

For comprehensive guidance on implementing secure cryptographic patterns using this extension, refer to the official guide: Using Libsodium in PHP Projects.

The libavifinfo C snippet is used to partially parse AVIF payloads to extract metadata. It provides a lightweight alternative to the full libavif library for determining specific image properties.

It can extract the following information from an AVIF image:

• Width
• Height
• Bit depth
• Channel count

libmbfl is a streamable multibyte character code filter and converter library. It is used within the PHP mbstring extension to handle various character encodings and conversions.

Note that the version bundled with PHP is a fork of the original libmbfl repository and is maintained directly within the php-src repository to support PHP-specific requirements.

The readline extension provides generic line editing, history, and tokenization functions. It is primarily intended for use in the CLI SAPI (Command Line Interface) to enhance interactive shell experiences.

For detailed API documentation and usage instructions, refer to the official PHP manual: https://www.php.net/manual/en/book.readline.php

The interpreter reads and executes opcodes using a three-address code format, where each instruction typically has one result and up to two operands. Both results and operands are handled as zvals.

• The complete list of opcodes is found in the generated Zend/zend_vm_opcodes.h.
• The specific behavior of each opcode is defined in Zend/zend_vm_def.h.

Execution Logic Example:

• JMPZ: If the first operand is 'falsy', jump to the instruction at the second operand's address. Otherwise, fall through to the next instruction.
• ECHO: Prints the first operand.
• RETURN: Terminates the current function.

PHP provides many essential bundled extensions. To add more functionality, you can use:

• PIE (the PHP Installer for Extensions): Recommended for installing additional extensions.
• PECL: The (now deprecated) PHP Extension Community Library.
• PIE Extensions list: A searchable list of available extensions on Packagist.

The config.m4 file uses M4 macros to define how the extension is built and configured. For a self-contained extension, you typically use PHP_ARG_ENABLE or PHP_ARG_WITH to handle configuration flags, and PHP_NEW_EXTENSION to define the extension name and its source files.

To ensure the extension can be loaded as a shared module, pass $ext_shared as the third argument to PHP_NEW_EXTENSION.

PHP_ARG_ENABLE([foobar],
  [whether to enable foobar],
  [AS_HELP_STRING([--enable-foobar],
    [Enable foobar])])

if test "$PHP_FOOBAR" != "no"; then
  PHP_NEW_EXTENSION([foobar], [foo.c bar.c], [$ext_shared])
fi

Stub files are PHP files containing only declarations (constants, classes, methods, functions) with empty bodies. They are used to define the interface of PHP symbols without implementing their logic. Stub files conventionally use the .stub.php extension and are processed by build/gen_stub.php to generate C code (arginfo, function entries, class entries) or documentation.

<?php
/** @var string */
const ANIMAL = "Elephant";

class Atmosphere {
    public function calculateBar(): float {}
}

function fahrenheitToCelsius(float $fahrenheit): float {}

The attributes field in a zend_constant is a HashTable that stores details about attributes applied to a constant.

Important Limitation: Attributes can only be added to constants declared at compile time using the const keyword (e.g., const EXAMPLE = 123;). They cannot be applied to constants defined at runtime using the define() function (e.g., define('EXAMPLE', 123);).