php数组排序和分割字符串

 function sortStr($str){

     $ary = str_split($str);
     sort($ary);
     $len = count($ary);

     $arr = array();
     for($i=0; $i<$len; $i++){
         $n = ceil($i/2);
         $k = ($i % 2 == 0) ? $len-1-$n : $n-1;
         $arr[] = $ary[$k];
     }

     return $arr;
 }

 $str = '952164387';
 print_r(sortStr($str));

// 输出结果

 Array
 (
     [0] => 9
     [1] => 1
     [2] => 8
     [3] => 2
     [4] => 7
     [5] => 3
     [6] => 6
     [7] => 4
     [8] => 5
 )