Not really no.
Your <form> has actually nothing to do with PHP. It's purely HTML, instructing the client's browser what sort of data your PHP code expects to receive.
Whether the browser is ultimately responsible for sending the request, or if the request is created by some other means, you can't really know.
Requests created by a browser can easily be duplicated and manipulated.
The best thing to do is just make sure that the data you are receiving is valid; making sure numbers are numbers, emails are emails, links are links, and so forth.
The
Variable handling Functions and
Regular Expressions are very helpful there.