PHP 7.4 FFI and function pointers via dlsym

ffi-dlsym-functions-pointer.php

<?php

declare(strict_types=1);

// see http://manpages.ubuntu.com/manpages/bionic/man3/dlsym.3.html
$ffi = FFI::cdef(
    "void *dlsym(void *handle, const char *symbol);"
);
$pointer = $ffi->dlsym(null, 'zend_write'); // it´s echo ...
$zend_write = FFI::new('void*(*)(...)'); // generic function pointer

FFI::memcpy(
    FFI::addr($zend_write),
    $pointer, // pointer to the function pointer
    FFI::sizeof($zend_write)
);
$zend_write('hello world' . PHP_EOL, 12);

// do the same via ffi binding
$php = FFI::cdef(
    "
    typedef int (*zend_write_func_t)(const char *str, size_t str_length);
    extern zend_write_func_t zend_write;
    "
);

$zend_write_ffi = $php->zend_write;
var_dump($zend_write_ffi == $zend_write);
$zend_write_ffi('hello world ffi' . PHP_EOL, 16);