Refactoring code test PHP

test-1.php

<?php

/**
 * Is the bar open
 *
 * @return bool 
 */
function isBarOpen($day)
{
    if ($day) {
        if (is_string($day)) {
            if ($day == 'friday' || $day == 'Friday') {
                return true;
            } elseif ($day == 'saturday' || $day == 'Saturday') {
                return true;
            } elseif ($day == 'sunday' || $day == 'Sunday') {
                return true;
            } else {
                return 0;
            }
        } else {
            return 0;
        }
    } else {
        return 0;
    }
   
}

Backward compatibility is not required.