using forms to add records to mysql database - block submit on entering

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I'm new to php(and HTML) and I'm trying to write some php code so that
I can
insert data into a mysql database using html forms.

I've got two text forms and a submit button. When entering data and
selecting 'submit' a new record in my database is created. So far so
good... But when I enter data in only one content and hit the enter
key a new record is created with one empty field. And that something
don't want to happen.

Is there a way to block the text-forms so only a record is added when
I hit the 'submit' button?

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