plug multiple leaks

(you need to destroy the zval before changing its type manually)

ext/filter/callback_filter.c

@@ -28,6 +28,7 @@ void php_filter_callback(PHP_INPUT_FILTER_PARAM_DECL)
 	if (!option_array || !zend_is_callable(option_array, IS_CALLABLE_CHECK_NO_ACCESS, &name)) {
 		php_error_docref(NULL TSRMLS_CC, E_WARNING, "First argument is expected to be a valid callback");
 		efree(name);
+		zval_dtor(value);
 		Z_TYPE_P(value) = IS_NULL;
 		return;
 	}

ext/filter/sanitizing_filters.c

@@ -180,6 +180,7 @@ void php_filter_string(PHP_INPUT_FILTER_PARAM_DECL)
 	Z_STRLEN_P(value) = new_len;
 
 	if (new_len == 0) {
+		zval_dtor(value);
 		Z_TYPE_P(value) = IS_NULL;
 		return;
 	}