比较多维数组中的两个 DATETIME 字段并返回一个值或索引

Question

我有一个用户表。我正在查看的每行有 2 个DATETIME。我将查看$lastLog 日期和$lastReceived（最后收到的潜在客户）并确定哪个更新并成为他们的$eligibleTime。然后，我们将寻找最旧的$eligibleTime 来选择应该接收线索的用户。我正在筛选用户，以确保他们在潜在客户所在的适当州获得许可，并且他们还没有达到每日配额。

我在想，也许我构建了错误的多维数组，应该将所有 $lastLog 日期和 $lastReceived 日期分组到它们自己的数组中并运行 max($array) 或类似的东西。

我怎么看这个？我使用以下方法构建了一个多维数组：

    $sql = "SELECT `lastLog`,`firstName`,`lastReceived` FROM customers";
    $sql = mysqli_query($conn,$sql);
    $result = array();
    while($line = mysqli_fetch_assoc($sql)){
      $result[] = $line;
    }

它正在返回以下数据：

> Array ( [0] => Array ( [lastLog] => 2015-06-12 02:00:00 [firstName] => Nathaniel [lastReceived] => 2015-06-12 05:16:10 ) [1] => Array ( [lastLog] => 2015-06-12 01:00:00 [firstName] => Ignacio [lastReceived] => 2015-06-01 10:00:00 ) [2] => Array ( [lastLog] => 2015-06-12 00:00:00 [firstName] => James [lastReceived] => 2015-06-08 00:00:00 ) [3] => Array ( [lastLog] => 2015-06-12 04:00:00 [firstName] => Robert [lastReceived] => 2015-06-10 00:00:00 ) ) 

谢谢你，纳特

Answer 1

感谢 Marc B，问题解决了。

$sql = mysqli_query($conn,
   "SELECT firstName, greatest(lastLog, lastReceived) AS eligibleTime 
    FROM customers 
    ORDER BY eligibleTime DESC
    LIMIT 1");
$result = mysqli_fetch_assoc($sql);
print_r($result);