Flatten multidimensional array concatenating keys [duplicate]

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'   => '[email protected]',
        'name'    => 'Super User',
        'address' => array(
            'billing' => 'Street 1',
            'delivery' => 'Street 2'
        )
    ),
    'post' => 'Hello, World!'
);

I want it flatten, transformed into:

$data = array(
    'user.email' => '[email protected]',
    '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
– J. Bruni, Commented Mar 3, 2012 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
– J. Bruni, Commented Mar 3, 2012 at 13:19
For those developing with Laravel, just enjoy its in-built methods. See Convert a multidimensional collection (array) to a flattened structure with dot-delimited keys in Laravel — mickmackusa
– mickmackusa ♦, Commented May 4, 2024 at 22:23

Felix Kling · Accepted Answer · 2012-03-03 12:39:51Z

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 3, 2012 at 12:39

Felix Kling

820k181 gold badges1.1k silver badges1.2k bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

user706420 Over a year ago

thank you! you also have the counterpart? create a multi-array from this flatten array?

Frantisek Hallo Over a year ago

you sir, thank you, shame it is the last answer in the order, almost did not notice it

J. Bruni · Accepted Answer · 2012-03-03 13:00:41Z

25

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;
}

edited Mar 3, 2012 at 13:00

answered Mar 3, 2012 at 12:55

J. Bruni

20.5k13 gold badges80 silver badges93 bronze badges

1 Comment

Studocwho Over a year ago

Works like a treat. Though if any child arrays use numeric keys, the function will still add the numeric key as the prefix, like user.2. To avoid this, I've just added a simple condition below the $new_key line to check if it is numeric to simply use the previous prefix. if ( is_numeric( $key ) ) { $new_key = $prefix; }

Basti · Accepted Answer · 2012-03-03 13:09:10Z

9

Try this

<?php

$data = array(
    'user' => array(
        'email'   => '[email protected]',
        '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 '[email protected]' (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 3, 2012 at 13:09

answered Mar 3, 2012 at 12:43

Basti

4,0511 gold badge21 silver badges22 bronze badges

6 Comments

J. Bruni Over a year ago

Really cool, and helpful. Thanks! I will suggest an edit (I removed the need of setting a root prefix).

J. Bruni Over a year ago

Hmmm, as I couldn't, I will post as a separated answer.

J. Bruni Over a year ago

+1 - Led me to the right path. I'd accepted it if didn't require a root prefix.

Basti Over a year ago

changed it a bit so it won't do an initial prefix.

Basti Over a year ago

ah nevermind. it's nearly the same as Felix Kling's solution.

|

Joseph · Accepted Answer · 2012-03-03 13:00:11Z

3

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);

edited Mar 3, 2012 at 13:00

answered Mar 3, 2012 at 12:54

Joseph

120k31 gold badges186 silver badges238 bronze badges

Comments

scibuff · Accepted Answer · 2012-03-03 12:49:41Z

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 3, 2012 at 12:49

answered Mar 3, 2012 at 12:44

scibuff

13.8k2 gold badges30 silver badges34 bronze badges

2 Comments

J. Bruni Over a year ago

Cool. +1 But I don't want to specify a root key.

scibuff Over a year ago

$flattened_key = ( empty( $parent_key ) ) ? $key : $parent_key . '.' . $key;

Collectives™ on Stack Overflow

Flatten multidimensional array concatenating keys [duplicate]

5 Answers 5

2 Comments

1 Comment

6 Comments

Comments

2 Comments

Linked

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

2 Comments

1 Comment

6 Comments

Comments

2 Comments

Linked

Related