php 多维数组简化（递归）

 <?php
     $a=[

         'a'=>['d'=>['aa'=>1,'bb'=>2,'cc'=>3]],
         'b'=>['f'=>['dd'=>4,'ee'=>5,'ff'=>6]],
         'c'=>['g'=>['gg'=>7,'hh'=>8,'ii'=>9]],
         ];

         $b=reduce_arr($a);
         echo '<pre>';
         var_dump($b);

  function reduce_arr ($arr) {

         static $temp = array(); // 声明了一个静态局部变量

         foreach ($arr as $key => $val) {
             if (is_array($val)) {
                 reduce_arr($val);
             } else {
                 $temp[$key] = $val;
             }
         }
         return $temp;
 }
  ?>