PHP 二維數組根據某個字段排序

要求：從兩個不一樣的表中獲取各自的4條數據，而後整合(array_merge)成一個數組，再根據數據的建立時間降序排序取前4條。

遇到這個要求的時候就不是 ORDER BY 能解決的問題了。所以翻看 PHP 手冊查找到了以下方法，作此筆記。

<?php
/**
 * 二維數組根據某個字段排序
 * 功能：按照用戶的年齡倒序排序
 * @author ruxing.li
 */
header('Content-Type:text/html;Charset=utf-8');
$arrUsers = array(
    array(
            'id'   => 1,
            'name' => '張三',
            'age'  => 25,
    ),
    array(
            'id'   => 2,
            'name' => '李四',
            'age'  => 23,
    ),
    array(
            'id'   => 3,
            'name' => '王五',
            'age'  => 40,
    ),
    array(
            'id'   => 4,
            'name' => '趙六',
            'age'  => 31,
    ),
    array(
            'id'   => 5,
            'name' => '黃七',
            'age'  => 20,
    ),
); 


$sort = array(
        'direction' => 'SORT_DESC', //排序順序標誌 SORT_DESC 降序；SORT_ASC 升序
        'field'     => 'age',       //排序字段
);
$arrSort = array();
foreach($arrUsers AS $uniqid => $row){
    foreach($row AS $key=>$value){
        $arrSort[$key][$uniqid] = $value;
    }
}
if($sort['direction']){
    array_multisort($arrSort[$sort['field']], constant($sort['direction']), $arrUsers);
}

var_dump($arrUsers);

/*
輸出結果：

array (size=5)
  0 => 
    array (size=3)
      'id' => int 5
      'name' => string '黃七' (length=6)
      'age' => int 20
  1 => 
    array (size=3)
      'id' => int 2
      'name' => string '李四' (length=6)
      'age' => int 23
  2 => 
    array (size=3)
      'id' => int 1
      'name' => string '張三' (length=6)
      'age' => int 25
  3 => 
    array (size=3)
      'id' => int 4
      'name' => string '趙六' (length=6)
      'age' => int 31
  4 => 
    array (size=3)
      'id' => int 3
      'name' => string '王五' (length=6)
      'age' => int 40

*/