Index: ext/standard/var.c
===================================================================
RCS file: /repository/php-src/ext/standard/var.c,v
retrieving revision 1.271
diff -u -r1.271 var.c
--- ext/standard/var.c	2 Nov 2007 09:43:04 -0000	1.271
+++ ext/standard/var.c	6 Nov 2007 19:22:24 -0000
@@ -1003,19 +1003,24 @@
 					ZVAL_ASCII_STRINGL(&fname, "__sleep", sizeof("__sleep") - 1, 1);
 					res = call_user_function_ex(CG(function_table), &struc, &fname, &retval_ptr, 0, 0, 1, NULL TSRMLS_CC);
 					zval_dtor(&fname);
-					if (res == SUCCESS && !EG(exception)) {
-						if (retval_ptr) {
-							if (HASH_OF(retval_ptr)) {
-								php_var_serialize_class(buf, struc, retval_ptr, var_hash TSRMLS_CC);
-							} else {
-								php_error_docref(NULL TSRMLS_CC, E_NOTICE, "__sleep should return an array only containing the names of instance-variables to serialize");
-								/* we should still add element even if it's not OK,
-								 * since we already wrote the length of the array before */
-								smart_str_appendl(buf,"N;", 2);
-							}
+
+					if (res == SUCCESS && !EG(exception) && retval_ptr) {
+						/* only serialize using the return value
+							if it's an array, allow NULLs to fall through */
+						if (HASH_OF(retval_ptr)) {
+							php_var_serialize_class(buf, struc, retval_ptr, var_hash TSRMLS_CC);
+							zval_ptr_dtor(&retval_ptr);
+							return;
+						} else if (Z_TYPE_P(retval_ptr) != IS_NULL) {
+							php_error_docref(NULL TSRMLS_CC, E_NOTICE, "__sleep should return an array "
+									 "containing the names of instance-variables to "
+									 "serialize, or NULL.");
+							/* we should still add element even if it's not OK,
+								since we already wrote the length of the array before */
+							smart_str_appendl(buf,"N;", 2);
 							zval_ptr_dtor(&retval_ptr);
+							return;
 						}
-						return;
 					}
 				}