ext_Ptr.cpp

#include "hphp/runtime/ext/extension.h"
#include "hphp/runtime/base/execution-context.h"
#include "hphp/runtime/vm/native-data.h"

void add(int *x, int *y, int *result) {
  *result = *x + *y;
}

namespace HPHP {

void HHVM_FUNCTION(add, VRefParam a, VRefParam b, VRefParam c) {
  int ta = a.toInt64();
  int tb = b.toInt64();
  int tc = 0;
  add(&ta, &tb, &tc);
  a.assignIfRef(ta);
  b.assignIfRef(tb);
  c.assignIfRef(tc);
}

class PtrExtension : public Extension {
 public:
  PtrExtension(): Extension("Ptr", "1.0") {}
  void moduleInit() override {
    HHVM_FE(add);
    loadSystemlib();
  }
} s_Ptr_extension;

HHVM_GET_MODULE(Ptr);
}

ext_Ptr.php

<?hh
<<__Native>>
function add(int &$a, int &$b, int &$c): void;

runme.php

<?php
	$a = 37;
	$b = 42;
	$c = 0;  // $c must be defined and not null.

	print "	a = $a\n";
	print "	b = $b\n";

	# Call the add() function wuth some pointers
	add($a, $b, $c);

	print " $a + $b = $c\n";
?>