如何获取多维数组中某个键的子键？

Question

array(
   'World'=>array(
            'Asia'=>array(
               'Japan'=>array(
                    'City'=>'Tokyo'
               )
          )
     )
);

In my array I am searching for a key:

foreach ($array as $key => $item) {
   if(is_array($item)){
      if (stripos($key, "Japan") !== false){
         echo $key;
      }
   }
}

The result is Japan .

For each key I want to check if the child key is "City". So I did the following:

   foreach ($array as $key => $item) {
       if(is_array($item)){
          if (stripos($key, "Japan") !== false){
             echo $key;
             foreach ($key as $k => $i) {
                if (stripos($k, "City") !== false){
                   echo "true";
               } else {
                   echo "false";
              }
          }
       }
    }

I expect the result Japan true or at least the result Japan false but the result is still only Japan I do not understand.

Answer 1

In your second foreach your using a single element ( $key ) while you should use a set of elements ( $array[$key] , considering it's a multidimensional array).

foreach ($array as $key => $item) {
       if(is_array($item)){
          if (stripos($key, "Japan") !== false){
             echo $key;
             foreach ($array[$key] as $k => $i) {
                if (stripos($k, "City") !== false){
                   echo "true";
               } else {
                   echo "false";
              }
          }
       }
    }

I'd go with a recursion algorithm to solve the problem:

function find_array_children_key($array, $children_key, $parent_key=''){
    $returning_value = false;
    if(is_array($array))
    {
        foreach($array as $key=>$value)
        {
            if($key===$children_key)
                $returning_value = $parent_key;
            else
                $returning_value = find_array_children_key($array,$children_key,$key);

            if($returning_value!==false)
                break;
        }
    }

    return $returning_value;
} 

Which you'd call, for instance in your case, find_array_children_key($array,'City')