Fixed issue laruence#40

Using absolute index could be error-prone, updated code to use relative indices as it commonly done with Lua

lua.c

@@ -321,8 +321,11 @@ zval *php_lua_get_zval_from_lua(lua_State *L, int index, zval *lua_obj, zval *rv
 			break;
 		case LUA_TTABLE:
 			array_init(rv);
+			lua_pushvalue(L, index); /* stack now contains: -1 => table */
+
 			lua_pushnil(L);  /* first key */
-			while (lua_next(L, index-1) != 0) {
+			/* stack now contains: -1 => nil; -2 => table */
+			while (lua_next(L, -2) != 0) {
 				zval key, val;
 
 				/* uses 'key' (at index -2) and 'value' (at index -1) */

tests/issue040.phpt

@@ -0,0 +1,19 @@
+--TEST--
+ISSUE #040 (segment fault)
+--SKIPIF--
+<?php
+if (!extension_loaded("lua")) print "skip lua extension missing";
+?>
+--FILE--
+<?php
+$lua = new Lua();
+$lua->eval(<<<CODE
+local a = {}
+print(a)
+CODE
+);
+?>
+--EXPECT--
+Array
+ (
+ )