Is there a MYSQL search limit?

Folks, I have a complicated search form that searches 15+ fields of a database table. I’ve linked all the searches with AND, eg: WHERE first_name LIKE ‘%$search1%’ AND but when I start to use greater than > or BETWEEN the whole thing throws out all fields. I just wondered if there was a limit to the amount of searches or I’m linking them in the wrong way?

Any advice as usual greatly appreciated.