function check_time($t1, $t2, $tn) {
    $t1 = +str_replace(":", "", $t1);
    $t2 = +str_replace(":", "", $t2);
    $tn = +str_replace(":", "", $tn);
    if ($t2 >= $t1) {
        return $t1 <= $tn && $tn < $t2;
    } else {
        return ! ($t2 <= $tn && $tn < $t1);
    }
}
$tests = array(
    array("16:00:00", "22:30:00", "15:00:00"),
    array("16:00:00", "22:30:00", "16:00:00"),
    array("16:00:00", "22:30:00", "22:29:59"),
    array("16:00:00", "22:30:00", "22:30:00"),
    array("16:00:00", "22:30:00", "23:59:59"),
    array("22:30:00", "16:00:00", "22:29:59"),
    array("22:30:00", "16:00:00", "22:30:00"),
    array("22:30:00", "16:00:00", "15:59:59"),
    array("22:30:00", "16:00:00", "16:00:00"),
    array("22:30:00", "16:00:00", "17:00:00")
);
foreach($tests as $test) {
    list($t1, $t2, $t0) = $test;
    echo "$t1 - $t2 contains $t0: " . (check_time($t1, $t2, $t0) ? "yes" : "no") . "\n";
}