Flatten multidimensional array concatenating keys

Question

Possible Duplicate:
PHP convert nested array to single array while concatenating keys?
Get array's key recursively and create underscore seperated string

Please, read the whole question before answering.

I have this multidimensional array:

$data = array(
    'user' => array(
        'email'   => 'user@example.com',
        'name'    => 'Super User',
        'address' => array(
            'billing' => 'Street 1',
            'delivery' => 'Street 2'
        )
    ),
    'post' => 'Hello, World!'
);

I want it flatten, transformed into:

$data = array(
    'user.email' => 'user@example.com',
    'user.name'  => 'Super User',
    'user.address.billing'  => 'Street 1',
    'user.address.delivery' => 'Street 2',
    'post'       => 'Hello, World!'
);

Important:

The keys are very important to me. I want them concatenated, separated by periods.
It should work with any level of nesting.

Thank you!

There are several similar questions, but I have not found a duplicate. — J. Bruni, Mar 03 '12 at 12:35
Indeed, there are two duplicates. I didn't know when asking. Anyway, all answers to them (except meagar's one) are far inferior than the ones given here now... they are unnecessarily complicated (using iterators, globals, classes, and the like, when it can be as simple as we can see here). — J. Bruni, Mar 03 '12 at 13:19

score 76 · Answer 1 · answered Mar 03 '12 at 12:39

76

Something like this should work:

function flatten($array, $prefix = '') {
    $result = array();
    foreach($array as $key=>$value) {
        if(is_array($value)) {
            $result = $result + flatten($value, $prefix . $key . '.');
        }
        else {
            $result[$prefix . $key] = $value;
        }
    }
    return $result;
}

DEMO

answered Mar 03 '12 at 12:39

Felix Kling

795,719
175
1,089
1,143

thank you! you also have the counterpart? create a multi-array from this flatten array? – user706420 Jun 26 '16 at 18:43
you sir, thank you, shame it is the last answer in the order, almost did not notice it – FantomX1 Sep 13 '18 at 11:32

J. Bruni · Accepted Answer · 2012-03-03T13:00:41.973

Thanks for all the given answers.

I have transformed it in the following, which is an improved version. It eliminates the need of a root prefix, does not need to use references, it is cleaner to read, and it has a better name:

function array_flat($array, $prefix = '')
{
    $result = array();

    foreach ($array as $key => $value)
    {
        $new_key = $prefix . (empty($prefix) ? '' : '.') . $key;

        if (is_array($value))
        {
            $result = array_merge($result, array_flat($value, $new_key));
        }
        else
        {
            $result[$new_key] = $value;
        }
    }

    return $result;
}

Basti · Answer 3 · 2012-03-03T13:09:10.287

9

Try this

<?php

$data = array(
    'user' => array(
        'email'   => 'user@example.com',
        'name'    => 'Super User',
        'address' => array(
            'billing' => 'Street 1',
            'delivery' => 'Street 2'
        )
    ),
    'post' => 'Hello, World!'
);

function prefixKey($prefix, $array)
{
    $result = array();
    foreach ($array as $key => $value)
    {
        if (is_array($value))
            $result = array_merge($result, prefixKey($prefix . $key . '.', $value));
        else
            $result[$prefix . $key] = $value;
    }   
    return $result;
}

var_dump(prefixKey('', $data));

?>

Outputs

array
  'user.email' => string 'user@example.com' (length=16)
  'user.name' => string 'Super User' (length=10)
  'user.address.billing' => string 'Street 1' (length=8)
  'user.address.delivery' => string 'Street 2' (length=8)
  'post' => string 'Hello, World!' (length=13)

edited Mar 03 '12 at 13:09

answered Mar 03 '12 at 12:43

Basti

3,998
1
18
21

Really cool, and helpful. Thanks! I will suggest an edit (I removed the need of setting a root prefix). – J. Bruni Mar 03 '12 at 12:50
Hmmm, as I couldn't, I will post as a separated answer. – J. Bruni Mar 03 '12 at 12:53
+1 - Led me to the right path. I'd accepted it if didn't require a root prefix. – J. Bruni Mar 03 '12 at 13:05
changed it a bit so it won't do an initial prefix. – Basti Mar 03 '12 at 13:09
ah nevermind. it's nearly the same as Felix Kling's solution. – Basti Mar 03 '12 at 13:13
upvote = 10 points, accept = 15 points; I thanked and gave points to everyone; although all you helped, I will accept my own answer (I receive no points) because it is the code I will actually USE – J. Bruni Mar 03 '12 at 13:22

Joseph · Answer 4 · 2012-03-03T13:00:11.163

test this out here

i passed by reference so no need for returns. just hand over the array storage.

$store = array();

function flatten($array,&$storage,$parentKey = ''){
    foreach($array as $key => $value){
    $itemKey = (($parentKey)? $parentKey.'.':'').$key;
        if(is_array($value)){
            flatten($value,$storage,$itemKey);
        } else {
            $storage[$itemKey] = $value;
        }
    }   
}

flatten($data,$store);
var_dump($store);

scibuff · Answer 5 · 2012-03-03T12:49:41.323

1

Use recursion such as this:

function process_data( $data, $parent_key ){

    if ( ! is_array( $data ) ){
        return $data;
    }

    $flattened_array = array();
    foreach( $data as $key => $item ){
        $flattened_key = $parent_key . '.' . $key;
        $flattened_array[ $flattened_key ] = process_data( $item, $flattened_key );
    }

    return $flattened_array;

}

edited Mar 03 '12 at 12:49

answered Mar 03 '12 at 12:44

scibuff

13,377
2
27
30

Cool. +1 But I don't want to specify a root key. – J. Bruni Mar 03 '12 at 12:54
`$flattened_key = ( empty( $parent_key ) ) ? $key : $parent_key . '.' . $key;` – scibuff Mar 03 '12 at 13:39

Flatten multidimensional array concatenating keys

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