$shop = array(
  0=>array(0=>1,1=>2,2=>3,3=>4)
  ,1=>array(0=>1,1=>2,2=>3)
  ,2=>array(0=>1,1=>2,2=>3)
  );
print_r($shop);
//示例 1:引用循环变量的地址赋值
foreach($shop as &$shoplist){
  $shoplist[] = '4444444444444';
  $shoplist['we'] = '欢迎光临编程素材网';
}
print_r($shop);

Array (
[0] => Array ( [0] => 1 [1] => 2 [2] => 3 [3] => 4 [4] => 4444444444444 [we] => 欢迎光临编程素材网 )
[1] => Array ( [0] => 1 [1] => 2 [2] => 3 [3] => 4444444444444 [we] => 欢迎光临编程素材网 )
[2] => Array ( [0] => 1 [1] => 2 [2] => 3 [3] => 4444444444444 [we] => 欢迎光临编程素材网 )
)

//示例2:修改循环变量数组,重新赋值
foreach($shop as $key=>$shoplist){
  $index = count($shoplist);
  $shoplist[$index] = '4444444444444';
  $shoplist['we'] = '欢迎光临编程素材网';
  $shop[$key]=$shoplist;
}
print_r($shop);

Array (
[0] => Array ( [0] => 1 [1] => 2 [2] => 3 [3] => 4 [4] => 4444444444444 [we] => 欢迎光临编程素材网 )
[1] => Array ( [0] => 1 [1] => 2 [2] => 3 [3] => 4444444444444 [we] => 欢迎光临编程素材网 )
[2] => Array ( [0] => 1 [1] => 2 [2] => 3 [3] => 4444444444444 [we] => 欢迎光临编程素材网 )
)