Implement GH-11934: Allow to pass CData into struct and/or union fields - #11935

<?php

echo "--- Callback return type --- \n";

$ffi = FFI::cdef('
typedef uint32_t (*test_callback)();
typedef struct {
	test_callback call_me;
} my_struct;
');

$struct = $ffi->new('my_struct');
$struct->call_me = function () use ($ffi) {
	$int = $ffi->new('uint32_t');
	$int->cdata = 42;
	return $int;
};

var_dump(($struct->call_me)());

echo "--- Other FFI\CData assignment ---\n";

$ffi = FFI::cdef('');

$source = $ffi->new('uint32_t');
$source->cdata = 123;
$target = $ffi->new('uint32_t');
$target->cdata = $source;

var_dump($target->cdata);

echo "--- Array element ---\n";

$ffi = FFI::cdef('');

$source = $ffi->new('uint32_t');
$source->cdata = 123;
$target = $ffi->new('uint32_t[1]');
$target[0] = $source;

var_dump($target[0]);

echo "--- Existing C variables --- \n";

$ffi = FFI::cdef(
	"int errno;",
	"libc.so.6"
);
$ffi->errno = 0;
var_dump($ffi->errno);
$source = $ffi->new('int');
$source->cdata = 31;
$ffi->errno = $source;
var_dump($ffi->errno);