What is the ruling on one who masturbates or practices the 'secret habit' (masturbation) during the daytime in Ramadan and performs ghusl before Maghrib? Is their fasting valid, and what is the expiation for them, both for the single and the married person?

Whoever masturbates during the daytime in Ramadan until ejaculation has invalidated his fast, and he must make up that day. His purification before sunset does not benefit him at all in the validity of his fast. The preponderant opinion is that expiation is not obligatory for him, whether he is married or single.