Update user meta when a payment has been made

update_user_meta.php

add_action('ms_gateway_transaction_log', 'update_meta_on_stripe_return' , 999, 8);

function update_meta_on_stripe_return( $id, $h, $is_paid, $sub, $iid, $amt, $n, $eid ) {
     mail('[email protected]', 'TEST',  "Was Paid : ".$is_paid);
       if( $is_paid )
           update_user_meta( $sub->user_id, 'some_meta', 'some_value' );
}