PHP 二维数组根据某个字段排序

要求：从两个不同的表中获取各自的4条数据，然后整合(array_merge)成一个数组，再根据数据的创建时间降序排序取前4条。

遇到这个要求的时候就不是 ORDER BY 能解决的问题了。因此翻看 PHP 手册查找到了如下方法，做此笔记。

<?php
/**
 * 二维数组根据某个字段排序
 * 功能：按照用户的年龄倒序排序
 * @author ruxing.li
 */
header('Content-Type:text/html;Charset=utf-8');
$arrUsers = array(
    array(
            'id'   => 1,
            'name' => '张三',
            'age'  => 25,
    ),
    array(
            'id'   => 2,
            'name' => '李四',
            'age'  => 23,
    ),
    array(
            'id'   => 3,
            'name' => '王五',
            'age'  => 40,
    ),
    array(
            'id'   => 4,
            'name' => '赵六',
            'age'  => 31,
    ),
    array(
            'id'   => 5,
            'name' => '黄七',
            'age'  => 20,
    ),
); 


$sort = array(
        'direction' => 'SORT_DESC', //排序顺序标志 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);

/*
输出结果：

array (size=5)
  0 => 
    array (size=3)
      'id' => int 5
      'name' => string '黄七' (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 '张三' (length=6)
      'age' => int 25
  3 => 
    array (size=3)
      'id' => int 4
      'name' => string '赵六' (length=6)
      'age' => int 31
  4 => 
    array (size=3)
      'id' => int 3
      'name' => string '王五' (length=6)
      'age' => int 40

*/