FFI — Foreign Function Interface (PHP 7.4)

TL;DR

Explanation

FFI::cdef(cDefinitions, libraryPath) creates an FFI object that wraps a shared library. You can then call C functions directly: $ffi->function_name($args). Data types: int, float, struct, pointer via FFI::new(). Use cases: accessing native libraries not wrapped as PHP extensions, performance-critical operations, system calls. Security: FFI requires ffi.enable=true in php.ini (disabled by default). Can also use FFI::load() with header files. Not suitable for most web applications — mainly for CLI tools and specialised integrations. Performance: overhead from PHP→C marshalling.

Common Misconception

Why It Matters

Common Mistakes

• Using FFI in web requests — security risk (ffi.enable should be restricted in FPM).
• Not handling pointer lifetimes — C memory is not garbage collected.
• Performance testing without accounting for FFI overhead.

Code Examples

// Extension-less library access — used to require a C extension

<?php
$ffi = FFI::cdef(
    'int abs(int j);',
    'libc.so.6'
);

$result = $ffi->abs(-42); // 42

// Working with structs:
$ffi = FFI::cdef('
    typedef struct { int x; int y; } Point;
', null);
$p = $ffi->new('Point');
$p->x = 10;

References

• ↗ https://www.php.net/manual/en/book.ffi.php

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