分享一段php获取任意时间的前一天代码

<?php
/**
 * 获取给定日期的前一天
 * @param string $date
 * @return string $yesterday
 */
function getYesterday($date)
{
    if(empty($date))
    {
        $yesterday = date("Y-m-d",strtotime("-1 day"));
    }else{
        $arr = explode('-', $date);
        $year = $arr[0];
        $month = $arr[1];
        $day = $arr[2];
        $unixtime = mktime(0,0,0,$month,$day,$year)-86400;
        $yesterday = date('Y-m-d',$unixtime);
    }
    return $yesterday;
}