function checkConflict($t1_start, $t1_end, $t2_start, $t2_end)
{
    if (convertToMin($t1_start) < convertToMin($t2_start)) {
        if (convertToMin($t1_end) > convertToMin($t2_start)) {
            return true;
        } else {
            return false;
        }
    } else {
        checkConflict($t2_start, $t2_end, $t1_start, $t1_end);
    }
}
 public function conflictBool($s)
 {
     //echo $this->time_start." ".$this->time_end." ".$s->time_start." ".$s->time_end."<br>";
     return checkConflict($this->time_start, $this->time_end, $s->time_start, $s->time_end);
 }