[RESOLVED] create new array from old array based on specific keys

stephdumais

Hello, I've been trying out a bunch of array functions to achieve this but I can't figure it out. I have a larger array i.e.:

['places']=>array(
            [0]=>array(
                    ['city']=>'Montreal',
                    ['province']=>'Quebec'
            ),
            [1]=>array(
                    ['city']=>'Toronto',
                    ['province']=>'Ontario'
            ),
            [2]=>array(
                    ['city']=>'Vancouver',
                    ['province']=>'British Columbia'
            ),
            [3]=>array(
                    ['city']=>'Ottawa',
                    ['province']=>'Ontario'
            )
)

From this array, I would like to create a smaller array based on, say, the 'province' key:

array('Quebec','Ontario','British Columbia','Ontario');

The tricky part, which isn't illustrated here, is that the larger array can contain the specified key at any level, so the function I'm looking for would obviously have to be recursive. I'm pretty sure there's a simple function I overlooked, right?
Much appreciated!

laserlight

Something like this might suffice:

function pullValuesWithKey($array, $search_key, &$result) {
    foreach ($array as $key => $value) {
        if (is_array($value)) {
            pullValuesWithKey($value, $search_key, $result);
        } else if ($key == $search_key) {
            $result[] = $value;
        }
    }
}

stephdumais

I added a return in the function to make it work 😉

function pullValuesWithKey($array, $search_key, &$result) {
    foreach ($array as $key => $value) {
        if (is_array($value)) {
            pullValuesWithKey($value, $search_key, $result);
        } else if ($key == $search_key) {
            $result[] = $value;
        }
    }
    return $result;
}

So I've tested this with a simple array and it works great. Unfortunately, it isnt returning an array with my real working array, which is more complex as it is generated from an xml file. I'll try to figure it out and post my results if it works, or get more answers from you with some samples 🙂

laserlight

stephdumais wrote:
I added a return in the function to make it work

You could do that, but the idea is to use $result as an out parameter, e.g.,

$result = array();
pullValuesWithKey($array, 'province', $result);

stephdumais wrote:
Unfortunately, it isnt returning an array with my real working array

Show the test input and output. If you are dealing with XML, you could consider using say, xpath, though I have no experience using that with PHP.

stephdumais

laserlight;10902452 wrote:
You could do that, but the idea is to use $result as an out parameter, e.g.,
$result = array();
pullValuesWithKey($array, 'province', $result);

Oh, I see now... so scratch the extra return then, it's working fine. Thank you.
I'm using a function which turns my xml data into an array. Using my previous example, the xml would look something like this:

<places>

<place>
	<city>Montreal</city>
	<province>Quebec</province>
</place>
<place>
	<city>Toronto</city>
	<province>Quebec</province>
</place>
<place>
	<city>Vancouver</city>
	<province>British Columbia</province>
</place>
<place>
	<city>Ottawa</city>
	<province>Ontario</province>
</place>

</places>

The function I'm using outputs this xml data as this array:

Array
(
    [places] => Array
        (
            [_c] => Array
                (
                    [place] => Array
                        (
                            [0] => Array
                                (
                                    [_c] => Array
                                        (
                                            [city] => Array
                                                (
                                                    [_v] => Montreal
                                                )
                                            [province] => Array
                                                (
                                                    [_v] => Quebec
                                                )
                                       )
                                )
                            [1] => Array
                                (
                                    [_c] => Array
                                        (
                                            [city] => Array
                                                (
                                                    [_v] => Toronto
                                                )
                                            [province] => Array
                                                (
                                                    [_v] => Quebec
                                                )
                                        )
                                )
                            [2] => Array
                                (
                                    [_c] => Array
                                        (
                                            [city] => Array
                                                (
                                                    [_v] => Vancouver
                                                )
                                            [province] => Array
                                                (
                                                    [_v] => British Columbia
                                                )
                                        )
                                )
                            [3] => Array
                                (
                                    [_c] => Array
                                        (
                                            [city] => Array
                                                (
                                                    [_v] => Ottawa
                                                )
                                            [province] => Array
                                                (
                                                    [_v] => Ontario
                                                )
                                        )
                                )
                        )
                )
        )
)

... so If I want to extract all the 'province' values from this generated array with your function, it doesn't work.

laserlight

stephdumais wrote:
... so If I want to extract all the 'province' values from this generated array with your function, it doesn't work.

The reason why it does not work is because I assumed that you only want non-array values in the final array. If that is not the case, then just swap the order of the checks:

function pullValuesWithKey($array, $search_key, &$result) {
    foreach ($array as $key => $value) {
        if ($key == $search_key) {
            $result[] = $value;
        } else if (is_array($value)) {
            pullValuesWithKey($value, $search_key, $result);
        }
    }
}

But now, what output do you expect for this array input?

$array = array('province' => array('province' => array('province' => 'X')));

One possibility is:

Array
(
    [0] => Array
        (
            [province] => Array
                (
                    [province] => X
                )

    )

[1] => Array
    (
        [province] => X
    )

[2] => X
)

But both my examples do not cater for this. However, catering for this is trivial, and if you understand what my code does you can make the change within seconds.

stephdumais

Yes I see how this complicates things. The other function makes a small array out of every value. I'll try to figure it out. Thanks for the help!

Weedpacket

Incidentally, processing the XML as XML would allow

foreach($document->getElementsByTagName('province') as $tag)
{
    $provinces[] = $tag->nodeValue;
}

stephdumais

Weedpacket;10902566 wrote:
Incidentally, processing the XML as XML would allow
foreach($document->getElementsByTagName('province') as $tag)
{
    $provinces[] = $tag->nodeValue;
}

Ah! Well, just goes to show how little I know about XML handling. I guess my other method was overkill. The above did the trick alright. Thanks Weedpacket!
I'm glad Laslight offered up her function as well though, as I've found used for it elsewhere. I think I will need to do some significant rewriting of my functions to take more advantage of the DOM method from now on.
Cheers!