PHP实现数组根据某个字段进行水平合并，横向合并案例分析

Array
(
  [0] => Array
    (
      [date] => 2019-04-02
      [today_pay_money] => 168.00
      [today_pay_num] => 1
      [yesterday_pay_money] => 999.00
      [yesterday_pay_num] => 1
    )
  [1] => Array
    (
      [date] => 2019-04-09
      [today_pay_money] => 0.01
      [today_pay_num] => 1
      [yesterday_pay_money] => 0.00
      [yesterday_pay_num] => 0
    )
  [2] => Array
    (
      [date] => 2019-05-05
      [today_pay_money] => 0.01
      [today_pay_num] => 1
      [yesterday_pay_money] => 2.00
      [yesterday_pay_num] => 1
    )
  [3] => Array
    (
      [date] => 2019-05-11
      [today_pay_money] => 0.00
      [today_pay_num] => 0
      [yesterday_pay_money] =>
      [yesterday_pay_num] => 1
    )
)

Array
(
  [0] => Array
    (
      [date] => 2019-05-07
      [today_pay_money1] => 0
      [today_pay_num1] => 0
      [yesterday_pay_money1] => 0
      [yesterday_pay_num1] => 0
    )
  [1] => Array
    (
      [date] => 2019-05-11
      [today_pay_money1] => 0
      [today_pay_num1] => 0
      [yesterday_pay_money1] => 1
      [yesterday_pay_num1] => 1
    )
)

Array
(
  [2019-04-02] => Array
    (
      [date] => 2019-04-02
      [today_pay_money] => 168.00
      [today_pay_num] => 1
      [yesterday_pay_money] => 999.00
      [yesterday_pay_num] => 1
    )
  [2019-04-09] => Array
    (
      [date] => 2019-04-09
      [today_pay_money] => 0.01
      [today_pay_num] => 1
      [yesterday_pay_money] => 0.00
      [yesterday_pay_num] => 0
    )
  [2019-05-05] => Array
    (
      [date] => 2019-05-05
      [today_pay_money] => 0.01
      [today_pay_num] => 1
      [yesterday_pay_money] => 2.00
      [yesterday_pay_num] => 1
    )
  [2019-05-11] => Array
    (
      [date] => 2019-05-11
      [today_pay_money] => 0.00
      [today_pay_num] => 0
      [yesterday_pay_money] =>
      [yesterday_pay_num] => 1
      [today_pay_money1] => 0
      [today_pay_num1] => 0
      [yesterday_pay_money1] => 1
      [yesterday_pay_num1] => 1
    )
  [2019-05-07] => Array
    (
      [date] => 2019-05-07
      [today_pay_money1] => 0
      [today_pay_num1] => 0
      [yesterday_pay_money1] => 0
      [yesterday_pay_num1] => 0
    )
)

$total = array_merge($a,$b));
$res = array();
foreach ($total as $k => $v) {
  if (empty($res[$v['date']]))
  $res[$v['date']] = $v;
  else
  $res[$v['date']]= array_merge($res[$v['date']],$v);
}