从日期数组中查找上一个和下一个最近的日期

Question

2017-02-10 00:00:00

我有一个日期数组

$date_array=array
(
    [0] => 2015-09-01 12:00:00
    [1] => 2015-12-01 12:00:00
    [2] => 2016-03-01 12:00:00
    [3] => 2016-06-01 12:00:00
    [4] => 2016-09-01 12:00:00
    [5] => 2016-12-01 12:00:00
    [6] => 2017-03-01 12:00:00
    [7] => 2017-06-01 12:00:00
    [8] => 2017-09-01 12:00:00
    [9] => 2017-12-01 12:00:00
    [10] => 2018-03-01 12:00:00
    [11] => 2018-06-01 12:00:00
    [12] => 2018-09-01 12:00:00
    [13] => 2018-12-01 12:00:00
    [14] => 2019-03-01 12:00:00
    [15] => 2019-06-01 12:00:00
    [16] => 2019-09-01 12:00:00
    [17] => 2019-12-01 12:00:00
    [18] => 2020-03-01 12:00:00
    [19] => 2020-06-01 12:00:00
);

所以我必须编写一个函数，它可以返回上一个(2016-12-01 12:00:00)和下一个(2017-03-01)日期。我怎样才能做到这一点

我写了比较日期的函数

function dif_date($date_1, $date_2) {
    $first= $date_1;
    $createDate = new DateTime($first);
    $strip = $createDate->format('Y-m-d');
    $difference = $date_2->diff($createDate, true);
    $difference->total_difference = $difference->y . "." . $difference->m;
    return $difference;
}

但我无法理解如何编写返回上一个和下一个日期的函数

Answer 1

尝试这个，

$date_array = array
    (
    '2015-09-01 12:00:00',
    '2015-12-01 12:00:00',
    '2016-03-01 12:00:00',
    '2016-06-01 12:00:00',
    '2016-09-01 12:00:00',
    '2016-12-01 12:00:00',
    '2017-03-01 12:00:00',
    '2017-06-01 12:00:00',
    '2017-09-01 12:00:00',
    '2017-12-01 12:00:00',
    '2018-03-01 12:00:00',
    '2018-06-01 12:00:00',
    '2018-09-01 12:00:00',
    '2018-12-01 12:00:00',
    '2019-03-01 12:00:00',
    '2019-06-01 12:00:00',
    '2019-09-01 12:00:00',
    '2019-12-01 12:00:00',
    '2020-03-01 12:00:00',
    '2020-06-01 12:00:00',
);

$date_prev = '';
$date_next = '';
$date = '2017-02-10 00:00:00';      

$ts_date = strtotime($date); // timestamp of the date we are comparing

foreach( $date_array as $da ){
    $ts_da = strtotime($da); // timestamp of the date from array
    $ts_prev = strtotime($date_prev); // timestamp of the previous date
    $ts_next = strtotime($date_next); // timestamp of the next date
    if( $ts_da < $ts_date && ( !$ts_prev || $ts_prev < $ts_da ) )
            $date_prev = $da;
    if( $ts_da > $ts_date && ( !$ts_next || $ts_next > $ts_da ) )
            $date_next = $da;
}

var_dump($date_prev); //string(19) "2016-12-01 12:00:00"
var_dump($date_next); //string(19) "2017-03-01 12:00:00"