/**
 * 获取同比上月的日期
 * 没有的取上月最后一天
 * @param $date
 * @return string
 */
function getTongBiDate($date){
    $time = strtotime($date);
    $start_date = date('Y-m-d', strtotime('-1 month', strtotime(date('Y-m', $time))));
    // 上个月的天数
    $lm_days = date('t', strtotime($start_date));
    //本月查的日期
    $day = date('d', $time);
    if($lm_days < $day){
        $tb_date = date('Y-m', strtotime($start_date))."-".$lm_days;
    }else{
        $tb_date = date('Y-m-d', strtotime('-1 month', $time));
    }
    return $tb_date;
}