// 函數(shù)式編程
$users = array(
  array('id' => 1, 'name' => 'abc1', 'age' => 29, '性別' => '男'),
  array('id' => 2, 'name' => 'abc2', 'age' => 21, '性別' => '女'),
  array('id' => 3, 'name' => 'abc3', 'age' => 23, '性別' => '男'),
  array('id' => 4, 'name' => 'abc4', 'age' => 25, '性別' => '女'),
  array('id' => 5, 'name' => 'abc5', 'age' => 20, '性別' => '女'),
  array('id' => 6, 'name' => 'abc6', 'age' => 24, '性別' => '男'),
  array('id' => 7, 'name' => 'abc7', 'age' => 28, '性別' => '女'),
  array('id' => 8, 'name' => 'abc8', 'age' => 27, '性別' => '男'),
);
//獲取性別為女的用戶
$arrayFilter = array_filter($users, function($item){
  return $item['性別'] == '女' ;
});
// 不影響原數(shù)組，返回一個新數(shù)組
$arrayMap = array_map(function($item){
  return array(
    'id' => $item['id'],
    'name' => $item['name'],
    'age' => $item['age'],
    'gender' => $item['性別'] == '男' ? 'male' : 'female',
  );
}, $users);
// 修改原數(shù)組，對年齡+10處理，同時(shí)新增索引gender，返回值 1 或 0
array_walk($users, function($item, $index){
  $item['gender'] = $item['性別'] == '男' ? 'male' : 'female';
  if ($index % 2 == 0) {
    $item['age'] += 10;
  }
});
//array_reduce(array $input , callable $function [,$initial = NULL ]) 用回調(diào)函數(shù)迭代地將數(shù)組簡化為單一的值
// 求最大年齡的用戶,返回最大年齡用戶信息
$arrayReduce = array_reduce($users, function($init, $val){
  return $init['age'] > $val['age'] ? $init : $val;
}, array('age' => 0));
// 求平均年齡
$avgAge = array_reduce($users, function($init, $item){
  return $init + $item['age'];
}, 0) / count($users);
/*
 * array_reduce 的內(nèi)部實(shí)現(xiàn)方式
function array_reduce($data, $callback, $initial) {
  foreach ($data as $index => $val) {
    $initial = $callback($initial, $val);
  }
  return $initial;
}
*/
//用array_map和array_mutisort來排序 
//利用array_map獲取要依據(jù)排序的數(shù)組,(匿名函數(shù) create_function($args, return $val))
//$arrField = array_map(create_function('$item', 'return $item["age"];'), $users); 【不推薦】
$arrField = array_map(function($item){
  return $item['age'];
}, $users);
//利用array_mutisort來進(jìn)行年齡從大到小排序
$arrSort = array_multisort($arrField, SORT_DESC, $users);

//閉包實(shí)現(xiàn)計(jì)數(shù)器
function counts() {
  $a = 1;
  // 閉包,引用變量$a
  return function() use($a) {
    return $a++;
  };
}
$countFunc = counts();
echo $countFunc(); // 1
echo $countFunc(); // 2
echo $countFunc(); // 3
echo $countFunc(); // 4