CSSgram | CSS library for Instagram filters | Widget library

There's a couple ways to handle this. I'm just going to show the one that's the simplest for me to write up.

To start, give $filter a default (empty) value if one hasn't been selected.

$filter = (!empty($_POST['filter']) ? $_POST['filter'] : ''); //filter select

Then, when you make the call to get and display the tweets, pass the selected filter value (if any).

tweets($user_id, 10, $filter); ?>

Update tweets.php to accept the filter as a parameter on the tweets() function (I'm also giving it a default value in the function definition in case you are calling it from other places).

public function tweets($user_id, $num, $filter = ''){

Finally, use this passed in value as the class value

An alternative would be to create a new function in your Tweet class called something like setFilter($filter). You would then call that function in main.php, passing in the selected filter, and access it within your Tweet class as $this->filter.