Already mentioned Heroku offers a free try-out. But I do not think you can set up a cron service on the free plan – you would have to refresh it manually.

There are also some dedicated free PHP hosts but they either inject ads or are otherwise unreliable.

You could also try VPS like DigitalOcean which offers a free credit often (for example in GitHub student pack), but that will require some knowledge of Linux administration.

I would recommend using some very cheap but reliable web host. I used to use Wedos before I could afford my own VPS.