phpc++ffi

PHP FFI - Convert void* to int

I have a C++ function, it casts int to void*.

void* get() {
  int a = 555;
  return (void*)a;
}

In my PHP code, I call this C++ function and want to convert its return value to int.

$ffi = FFI::cdef(
  "void* get();",
  "dllpath");

$voidptr = $ffi->get();

// convert void* to int

FFI::cast("int", $voidptr) does not work. The only successful method I tried was to print the $voidptr through print_r($voidptr, true);, and then get the int value through regular matching. Is there any other better way?

thanks for your help.

Solution

  • There are 2 methods:

    1. Declare the return value as int:

      $ffi = FFI::cdef(
       "int get();",
       "dllpath");
$intval = $ffi->get();

    2. Create a nullptr and subtract it:

      $nullptr = $ffi->cast('void*', 0);
$intval = $voidptr - $nullptr;