Index: Zend/zend.h
===================================================================
RCS file: /repository/ZendEngine2/zend.h,v
retrieving revision 1.293.2.11.2.3
diff -u -p -d -r1.293.2.11.2.3 zend.h
--- Zend/zend.h	19 May 2006 06:09:14 -0000	1.293.2.11.2.3
+++ Zend/zend.h	6 Jun 2006 17:49:26 -0000
@@ -365,6 +365,7 @@ struct _zend_class_entry {
 	zend_uint doc_comment_len;
 
 	struct _zend_module_entry *module;
+	zend_bool inherited;
 };
 
 #include "zend_stream.h"
Index: Zend/zend_compile.c
===================================================================
RCS file: /repository/ZendEngine2/zend_compile.c,v
retrieving revision 1.647.2.27.2.11
diff -u -p -d -r1.647.2.27.2.11 zend_compile.c
--- Zend/zend_compile.c	6 Jun 2006 14:17:21 -0000	1.647.2.27.2.11
+++ Zend/zend_compile.c	6 Jun 2006 17:49:27 -0000
@@ -2182,6 +2182,7 @@ ZEND_API void zend_do_inherit_interfaces
 
 	/* and now call the implementing handlers */
 	while (ce_num < ce->num_interfaces) {
+		ce->interfaces[ce_num]->inherited = 1;
 		do_implement_interface(ce, ce->interfaces[ce_num++] TSRMLS_CC);
 	}
 }
@@ -2247,6 +2248,20 @@ static zend_bool do_inherit_constant_che
 
 ZEND_API void zend_do_implement_interface(zend_class_entry *ce, zend_class_entry *iface TSRMLS_DC)
 {
+	zend_uint i, if_num = ce->num_interfaces, cnt = 0;
+
+	for (i = 0; i < if_num; i++) {
+		if (ce->interfaces[i] != NULL && ce->interfaces[i]->name_length == iface->name_length && !memcmp(ce->interfaces[i]->name, iface->name, iface->name_length)) {
+			cnt++;
+			if (cnt > 1 && ce->interfaces[i]->inherited != 0) {
+				/* the interface was previously inherited, ignoring */
+				return;
+			} else if (cnt > 1) {
+				zend_error(E_COMPILE_ERROR, "Cannot implement previously implemented interface %s", iface->name);
+			}
+		}
+	}
+
 	zend_hash_merge_ex(&ce->constants_table, &iface->constants_table, (copy_ctor_func_t) zval_add_ref, sizeof(zval *), (merge_checker_func_t) do_inherit_constant_check, iface);
 	zend_hash_merge_ex(&ce->function_table, &iface->function_table, (copy_ctor_func_t) do_inherit_method, sizeof(zend_function), (merge_checker_func_t) do_inherit_method_check, ce);
 
@@ -4070,6 +4085,7 @@ ZEND_API void zend_initialize_class_data
 
 	ce->doc_comment = NULL;
 	ce->doc_comment_len = 0;
+	ce->inherited = 0;
 
 	zend_hash_init_ex(&ce->default_properties, 0, NULL, zval_ptr_dtor_func, persistent_hashes, 0);
 	zend_hash_init_ex(&ce->properties_info, 0, NULL, (dtor_func_t) (persistent_hashes ? zend_destroy_property_info_internal : zend_destroy_property_info), persistent_hashes, 0);