$arr =  $tickets_info;（这里的arr打印出来是2维数组）
$flag = array(); 
foreach ($arr as $v) {
    $flag[] = $v['start_time'];
}
array_multisort($flag, SORT_ASC, $arr);

foreach ($arr as $k=>$v) {
    $v['start_time'] = substr($v['start_time'],5,11);
    $arr[$k]['start_time'] = $v['start_time'];
}