Change the serialization semantics to:

* if a certain object is of class INCOMPLETE_CLASS, the serializer will
    lookup the previously stored original class name of that object, and
    use that class name to serialize the object.

Change the deserialization semantics to:

  * if the class of an object, which is to be instantiated, is not found
    in the current context, the class name will be stored for later
    retrieval, and the class of that object is changed to INCOMPLETE_CLASS.

All function calls, property gets, and property sets operating on an
object of class INCOMPLETE_CLASS cause the execution to halt and to
output an informative error message.

ext/standard/basic_functions.c

@@ -708,6 +708,7 @@ PHP_RINIT_FUNCTION(basic)
 	BG(locale_string) = NULL;
 	BG(user_compare_func_name) = NULL;
 	BG(array_walk_func_name) = NULL;
+	BG(incomplete_class) = NULL;
 	BG(page_uid) = -1;
 	BG(page_inode) = -1;
 	BG(page_mtime) = -1;

ext/standard/basic_functions.h

@@ -170,6 +170,9 @@ typedef struct {
 	/* syslog.c */
 	int syslog_started;
 	char *syslog_device;
+
+	/* var.c */
+	zend_class_entry *incomplete_class;
 } php_basic_globals;
 
 #ifdef ZTS

ext/standard/var.c

@@ -14,6 +14,7 @@
    +----------------------------------------------------------------------+
    | Authors: Jani Lehtimäki <jkl@njet.net>                               |
    |          Thies C. Arntzen <thies@digicol.de>                         |
+   |          Sascha Schumann <sascha@schumann.cx>                        |
    +----------------------------------------------------------------------+
  */
 
@@ -29,6 +30,7 @@
 #include "php.h"
 #include "php_string.h"
 #include "php_var.h"
+#include "basic_functions.h"
 
 #define COMMON ((*struc)->is_ref?"&":"")
 
@@ -50,6 +52,101 @@ static int php_array_element_dump(zval **zv, int num_args, va_list args, zend_ha
 	return 0;
 }
 
+static char *php_lookup_class_name(zval **object, size_t *nlen, zend_bool del);
+
+#define INCOMPLETE_CLASS_MSG \
+		"The script tried to execute a method or "  \
+		"access a property of an incomplete object. " \
+		"Please ensure that the class definition <b>%s</b> of the object " \
+		"you are trying to operate on was loaded _before_ " \
+		"the session was started"
+
+static void incomplete_class_message(zend_property_reference *ref)
+{
+	char buf[1024];
+	char *class_name;
+
+	class_name = php_lookup_class_name(&ref->object, NULL, 0);
+	
+	if (!class_name)
+		class_name = estrdup("unknown");
+	
+	snprintf(buf, 1023, INCOMPLETE_CLASS_MSG, class_name);
+	
+	efree(class_name);
+
+	php_error(E_ERROR, buf);
+}
+
+static void incomplete_class_call_func(INTERNAL_FUNCTION_PARAMETERS, zend_property_reference *property_reference)
+{
+	incomplete_class_message(property_reference);
+}
+
+static int incomplete_class_set_property(zend_property_reference *property_reference, zval *value)
+{
+	incomplete_class_message(property_reference);
+	
+	/* does not reach this point */
+	return (0);
+}
+
+static zval incomplete_class_get_property(zend_property_reference *property_reference)
+{
+	zval foo;
+	
+	incomplete_class_message(property_reference);
+
+	/* does not reach this point */
+	return (foo);
+}
+
+#define INCOMPLETE_CLASS "__PHP_Incomplete_Class"
+
+static void php_create_incomplete_class(BLS_D)
+{
+	zend_class_entry incomplete_class;
+
+	INIT_OVERLOADED_CLASS_ENTRY(incomplete_class, INCOMPLETE_CLASS, NULL,
+			incomplete_class_call_func,
+			incomplete_class_get_property,
+			incomplete_class_set_property);
+
+	BG(incomplete_class) = zend_register_internal_class(&incomplete_class);
+}
+
+#define MAGIC_MEMBER "__PHP_Incomplete_Class_Name"
+
+static char *php_lookup_class_name(zval **object, size_t *nlen, zend_bool del)
+{
+	zval **val;
+	char *retval = NULL;
+
+	if (zend_hash_find((*object)->value.obj.properties, MAGIC_MEMBER, sizeof(MAGIC_MEMBER), (void **) &val) == SUCCESS) {
+		retval = estrndup(Z_STRVAL_PP(val), Z_STRLEN_PP(val));
+
+		if (nlen)
+			*nlen = Z_STRLEN_PP(val);
+
+		if (del)
+			zend_hash_del((*object)->value.obj.properties, MAGIC_MEMBER, sizeof(MAGIC_MEMBER));
+	}
+
+	return (retval);
+}
+
+static void php_store_class_name(zval **object, const char *name, size_t len)
+{
+	zval *val;
+
+	MAKE_STD_ZVAL(val);
+
+	Z_TYPE_P(val)   = IS_STRING;
+	Z_STRVAL_P(val) = estrndup(name, len);
+	Z_STRLEN_P(val) = len;
+
+	zend_hash_update((*object)->value.obj.properties, MAGIC_MEMBER, sizeof(MAGIC_MEMBER), &val, sizeof(val), NULL);
+}
 
 void php_var_dump(pval **struc, int level)
 {
@@ -149,6 +246,24 @@ PHP_FUNCTION(var_dump)
 	strcat(__p->value.str.val + __i, (S));\
 }
 
+#define PHP_SET_CLASS_ATTRIBUTES() 				\
+	if ((*struc)->value.obj.ce == BG(incomplete_class)) {				\
+		class_name = php_lookup_class_name(struc, &name_len, 1);		\
+		free_class_name = 1;											\
+	} else {															\
+		class_name = (*struc)->value.obj.ce->name;						\
+		name_len   = (*struc)->value.obj.ce->name_length;				\
+	}
+
+#define PHP_CLEANUP_CLASS_ATTRIBUTES()									\
+	if (free_class_name) efree(class_name)
+
+#define PHP_CLASS_ATTRIBUTES											\
+	char *class_name;													\
+	size_t name_len;													\
+	zend_bool free_class_name = 0										\
+
+
 /* }}} */
 /* {{{ php_var_serialize */
 
@@ -158,6 +273,7 @@ void php_var_serialize(pval *buf, pval **struc)
 	ulong slen;
 	int i;
 	HashTable *myht;
+	BLS_FETCH();
 
 	switch ((*struc)->type) {
 		case IS_BOOL:
@@ -202,6 +318,7 @@ void php_var_serialize(pval *buf, pval **struc)
 				zval *retval_ptr = NULL;
 				zval *fname;
 				int res;
+				PHP_CLASS_ATTRIBUTES;
 				CLS_FETCH();
 
 				MAKE_STD_ZVAL(fname);
@@ -212,7 +329,11 @@ void php_var_serialize(pval *buf, pval **struc)
 				if (res == SUCCESS) {
 					if (retval_ptr && HASH_OF(retval_ptr)) {
 						int count = zend_hash_num_elements(HASH_OF(retval_ptr));
-						slen = sprintf(s, "O:%d:\"%s\":%d:{",(*struc)->value.obj.ce->name_length,(*struc)->value.obj.ce->name, count);
+						
+						PHP_SET_CLASS_ATTRIBUTES();
+						slen = sprintf(s, "O:%d:\"%s\":%d:{",name_len,class_name, count);
+						PHP_CLEANUP_CLASS_ATTRIBUTES();
+						
 						STR_CAT(buf, s, slen);
 						if (count > 0) {
 							char *key;
@@ -268,7 +389,11 @@ void php_var_serialize(pval *buf, pval **struc)
 			if ((*struc)->type == IS_ARRAY) {
 				slen = sprintf(s, "a:%d:{", i);
 			} else {
-				slen = sprintf(s, "O:%d:\"%s\":%d:{",(*struc)->value.obj.ce->name_length,(*struc)->value.obj.ce->name, i);
+				PHP_CLASS_ATTRIBUTES;
+
+				PHP_SET_CLASS_ATTRIBUTES();
+				slen = sprintf(s, "O:%d:\"%s\":%d:{",name_len,class_name,i);
+				PHP_CLEANUP_CLASS_ATTRIBUTES();
 			}
 			STR_CAT(buf, s, slen);
 			if (i > 0) {
@@ -329,6 +454,7 @@ int php_var_unserialize(pval **rval, const char **p, const char *max)
 	char cur;
 	HashTable *myht;
 	ELS_FETCH();
+	BLS_FETCH();
 
 	switch (cur = **p) {
 		case 'N':
@@ -413,7 +539,11 @@ int php_var_unserialize(pval **rval, const char **p, const char *max)
 
 		case 'a':
 		case 'o':
-		case 'O': 
+		case 'O': {
+			zend_bool incomplete_class = 0;
+			char *class_name = NULL;
+			size_t name_len = 0;
+			
 			INIT_PZVAL(*rval);
 
 			if (cur == 'a') {
@@ -424,8 +554,6 @@ int php_var_unserialize(pval **rval, const char **p, const char *max)
 				zend_class_entry *ce;
 
 				if (cur == 'O') { /* php4 serialized - we get the class-name */
-					char *class_name;
-
 					if (*((*p) + 1) != ':') {
 						return 0;
 					}
@@ -437,7 +565,7 @@ int php_var_unserialize(pval **rval, const char **p, const char *max)
 					if (**p != ':') {
 						return 0;
 					}
-					i = atoi(q);
+					name_len = i = atoi(q);
 					if (i < 0 || (*p + 3 + i) > max || *((*p) + 1) != '\"' ||
 						*((*p) + 2 + i) != '\"' || *((*p) + 3 + i) != ':') {
 						return 0;
@@ -451,17 +579,23 @@ int php_var_unserialize(pval **rval, const char **p, const char *max)
 					(*p) += i;
 					
 					if (zend_hash_find(EG(class_table), class_name, i+1, (void **) &ce)==FAILURE) {
-						php_error(E_NOTICE, "Unserializing non-existant class: %s! No methods will be available!", class_name);
+						incomplete_class = 1;
-						ce = &zend_standard_class_def;
+						if (BG(incomplete_class) == NULL)
+							php_create_incomplete_class(BLS_C);
+						ce = BG(incomplete_class);
 					}
-
-					efree(class_name);
 				} else { /* old php 3.0 data 'o' */
 					ce = &zend_standard_class_def;
 				}
 
 				object_init_ex(*rval,ce);
 				myht = (*rval)->value.obj.properties;
+
+				if (incomplete_class)
+					php_store_class_name(rval, class_name, name_len);
+
+				if (class_name)
+					efree(class_name);
 			}
 
 			(*p) += 2;
@@ -527,6 +661,7 @@ int php_var_unserialize(pval **rval, const char **p, const char *max)
 
 			return *((*p)++) == '}';
 		  }
+	}
 
 	return 0;
 }