PHP if condition: Logical operators for filter from a form

I'm working with a form using the <datalist> tag, I have two input tags getting information from two different arrays. Below the form there is a Kanban board, the objective of the form is to serve as a filter, so when a user fills any of the inputs (or both) the board with fill accordingly.

Here is the problem: I had made two if staments (one for input) that work great when I use them alone but that I don't know how to put together because I don't know how to check which of the inputs has been filled (for that I believe I may have to use the issset() function), then if only one of them is used I need to use the || logical operator between them but if both are filled I need to use the && operator.

Using this condition (|| logical operator):

if (($tasksArray[$i]["responsible-party-names"] == $_POST['members'] && isset($_POST['members']))  ||
(($tasksArray[$i]['project-name'] == $_POST['projects'] && isset($_POST['projects']))))

If I fill only the members input it returns what it should.

If I fill only the projects input it returns all the projects in the array (although when using the if condition without the left part it works well).

Finally, if I fill both inputs I get the right project but all the team members.

What would be the simplest way to get it right?