Allow unserializer_callback_func to be turned off.

ext/standard/var_unserializer.c

@@ -393,7 +393,7 @@ yy20:
 	}
 
 	if (zend_hash_find(CG(class_table), class_name, len2 + 1, (void **) &ce) != SUCCESS) {
-		if (PG(unserialize_callback_func) == NULL) {
+		if ((PG(unserialize_callback_func) == NULL) || (PG(unserialize_callback_func)[0] == '\0')) {
 			incomplete_class = 1;
 			ce = PHP_IC_ENTRY;
 		} else {

ext/standard/var_unserializer.re

@@ -356,7 +356,7 @@ PHPAPI int php_var_unserialize(UNSERIALIZE_PARAMETER)
 	}
 
 	if (zend_hash_find(CG(class_table), class_name, len2 + 1, (void **) &ce) != SUCCESS) {
-		if (PG(unserialize_callback_func) == NULL) {
+		if ((PG(unserialize_callback_func) == NULL) || (PG(unserialize_callback_func)[0] == '\0')) {
 			incomplete_class = 1;
 			ce = PHP_IC_ENTRY;
 		} else {

main/main.c

@@ -239,7 +239,7 @@ PHP_INI_BEGIN()
 	STD_PHP_INI_BOOLEAN("track_errors",			"0",		PHP_INI_ALL,		OnUpdateBool,			track_errors,			php_core_globals,	core_globals)
 	STD_PHP_INI_BOOLEAN("y2k_compliance",		"0",		PHP_INI_ALL,		OnUpdateBool,			y2k_compliance,			php_core_globals,	core_globals)
 
-	STD_PHP_INI_ENTRY("unserialize_callback_func",	NULL,		PHP_INI_ALL,		OnUpdateStringUnempty,	unserialize_callback_func,	php_core_globals,	core_globals)
+	STD_PHP_INI_ENTRY("unserialize_callback_func",	NULL,		PHP_INI_ALL,		OnUpdateString,	unserialize_callback_func,	php_core_globals,	core_globals)
 	STD_PHP_INI_ENTRY("arg_separator.output",	"&",		PHP_INI_ALL,		OnUpdateStringUnempty,	arg_separator.output,	php_core_globals,	core_globals)
 	STD_PHP_INI_ENTRY("arg_separator.input",	"&",		PHP_INI_SYSTEM|PHP_INI_PERDIR,	OnUpdateStringUnempty,	arg_separator.input,	php_core_globals,	core_globals)