Software maintenance is one of the main quality characteristics of the software product. The maintainability of a system is a measure of the ability of the system to undergo maintenance or to return to normal operation after a failure. In this paper, a new model to improve the maintainability of object-oriented software has been proposed. The proposed model is based on newer versions of software quality standard and it is according to the measurement of several new metric. This model has been evaluated on famous PHP framework and the results showed that the proposed model is effective compared with the previous models.