// 函数式编程
$users = array(
  array('id' => 1, 'name' => 'abc1', 'age' => 29, '性别' => '男'),
  array('id' => 2, 'name' => 'abc2', 'age' => 21, '性别' => '女'),
  array('id' => 3, 'name' => 'abc3', 'age' => 23, '性别' => '男'),
  array('id' => 4, 'name' => 'abc4', 'age' => 25, '性别' => '女'),
  array('id' => 5, 'name' => 'abc5', 'age' => 20, '性别' => '女'),
  array('id' => 6, 'name' => 'abc6', 'age' => 24, '性别' => '男'),
  array('id' => 7, 'name' => 'abc7', 'age' => 28, '性别' => '女'),
  array('id' => 8, 'name' => 'abc8', 'age' => 27, '性别' => '男'),
);
//获取性别为女的用户
$arrayFilter = array_filter($users, function($item){
  return $item['性别'] == '女' ;
});
// 不影响原数组，返回一个新数组
$arrayMap = array_map(function($item){
  return array(
    'id' => $item['id'],
    'name' => $item['name'],
    'age' => $item['age'],
    'gender' => $item['性别'] == '男' "age"];'), $users); 【不推荐】
$arrField = array_map(function($item){
  return $item['age'];
}, $users);
//利用array_mutisort来进行年龄从大到小排序
$arrSort = array_multisort($arrField, SORT_DESC, $users);

//闭包实现计数器
function counts() {
  $a = 1;
  // 闭包,引用变量$a
  return function() use(&$a) {
    return $a++;
  };
}
$countFunc = counts();
echo $countFunc(); // 1
echo $countFunc(); // 2
echo $countFunc(); // 3
echo $countFunc(); // 4