Question

All,

I have the following array and function, which will create a multidimensional array based on array key’s that you specific. For every attribute you pass to the function, it will add another dimension to the array. Think of it as array sorting.

The function supplied works great, but it uses eval, I had a hard time coming up with a function which was consistent and threw no errors without it.

Let’s start with an array:

$array = array(
          array(‘name’ => ‘Person1’, ‘username’ => ‘username1’, ‘join_date’ => 12233445566, ‘state’ => ‘NJ’),
          array(‘name’ => ‘Person2’, ‘username’ => ‘username2’, ‘join_date’ => 12233445566, ‘state’ => ‘NJ’),
          array(‘name’ => ‘Person3’, ‘username’ => ‘username3’, ‘join_date’ => 12233445996, ‘state’ => ‘NY’),
          array(‘name’ => ‘Person4’, ‘username’ => ‘username4’, ‘join_date’ => 12233445996, ‘state’ => ‘NJ’),
          array(‘name’ => ‘Person5’, ‘username’ => ‘username5’, ‘join_date’ => 12233445566, ‘state’ => ‘NJ’),
          array(‘name’ => ‘Person6’, ‘username’ => ‘username6’, ‘join_date’ => 12233445566, ‘state’ => ‘NY’),
          array(‘name’ => ‘Person7’, ‘username’ => ‘username7’, ‘join_date’ => 12233445776, ‘state’ => ‘NY’),
          array(‘name’ => ‘Person8’, ‘username’ => ‘username8’, ‘join_date’ => 12233445566, ‘state’ => ‘NY’),
          array(‘name’ => ‘Person9’, ‘username’ => ‘username9’, ‘join_date’ => 12233445996, ‘state’ => ‘NJ’),
);

Here is an example function:

function createIndex($array, $index){
   $index_array = array();

   foreach($array as $result){

          if(is_array($index)){
                 $key = '$index_array';
                 for($i=0;$i<=sizeof($index)-1;$i++){
                       $key .= "['{$result[$index[$i]]}']";
                 }
                 $key .= "[]"; 
                 eval("$key = \$result;");
          }
          else{
                 $index_array[$result[$index]] = $result; 
          }
   }

   return $index_array;
}

The Calling function:

print_r(create_index($array, array(‘state’, ‘join_date’)));

The desired output:

Array
(
[NJ] => Array
    (
        [12233445566] => Array
            (
                [0] => Array
                    (
                        [name] => Person1
                        [username] => username1
                        [join_date] => 12233445566
                        [state] => NJ
                    )

                [1] => Array
                    (
                        [name] => Person2
                        [username] => username2
                        [join_date] => 12233445566
                        [state] => NJ
                    )

                [2] => Array
                    (
                        [name] => Person5
                        [username] => username5
                        [join_date] => 12233445566
                        [state] => NJ
                    )

            )

        [12233445996] => Array
            (
                [0] => Array
                    (
                        [name] => Person4
                        [username] => username4
                        [join_date] => 12233445996
                        [state] => NJ
                    )

                [1] => Array
                    (
                        [name] => Person9
                        [username] => username9
                        [join_date] => 12233445996
                        [state] => NJ
                    )

            )

    )

[NY] => Array
    (
        [12233445996] => Array
            (
                [0] => Array
                    (
                        [name] => Person3
                        [username] => username3
                        [join_date] => 12233445996
                        [state] => NY
                    )

            )

        [12233445566] => Array
            (
                [0] => Array
                    (
                        [name] => Person6
                        [username] => username6
                        [join_date] => 12233445566
                        [state] => NY
                    )

                [1] => Array
                    (
                        [name] => Person8
                        [username] => username8
                        [join_date] => 12233445566
                        [state] => NY
                    )

            )

        [12233445776] => Array
            (
                [0] => Array
                    (
                        [name] => Person7
                        [username] => username7
                        [join_date] => 12233445776
                        [state] => NY
                    )

            )

    )

)

The question: What are ways that you would conquer the above to obtain the same results form the same array? I am curious to see how others would do it.

Thanks

Answer 1

Using references, I was able to come up with the below function. It works great!

It will automatically detect if multiple leafs exist at the end of the tree, and if so, branch, or leaf itself. Also, you can merge, using the $merge_classifier argument. This will allow you to merge columns called count for example, which will add the values together.

function createIndex($keys, Array $array, $merge_classifier = NULL, $return_array = array())
{               

    if(is_string($keys)){
        $tmp = $keys;
        $keys = array();
        $keys[] = $tmp; 
    }

    foreach($array as $result) {
        $object = &$return_array;

        foreach($keys as $index){
            if(!array_key_exists($result[$index], $object)) {
                $object[$result[$index]] = array();
            }
            $object = &$object[$result[$index]];
        }

        if(!is_null($merge_classifier)){
            $object = array_merge($result, array($merge_classifier => ($result[$merge_classifier] + $object[$merge_classifier])));
        }
        else{
            if(sizeof($object) > 0){
                $object[] = $result;    
            }else{
                $object = $result;  
            }
        }
    }

    return $return_array;
}