Reduce Array Information

Question

I am pulling a large amount of data from a web service which gives me back a multidimensional mixed array where I only need 10% of information from. I am looking for a flexible way to keep only the information needed for my purposes.

I did not find a PHP function or method to do that.

Don't get me wrong, I don't want to filter values and I don't want to slice elements.

Putting it into a database perspective, I want to "simply" drop some columns. Or better: I want to keep columns I need and drop all the others which I don't need and I don't know.

E.G.

$big_array = array(
array("year" => 1979, "name" => "Miller",   "wage" => "100", "children"=>array("John", "Kate")),
array("year" => 1983, "name" => "Smith",  "wage" => "200"),
array("year" => 1980, "name" => "Mayer",  "wage" => "200", "children"=>array("Tom")),
array("year" => 1981, "name" => "Mayer",  "wage" => "100"),
array("year" => 1980, "name" => "Clinton", "wage" => "300", "children"=>array("Rosa", "Dick", "Christine")),
array("year" => 1981, "name" => "Bush", "wage" => "200"));
print_r($big_array);

Will give me this:

Array
(
    [0] => Array
        (
            [year] => 1979
            [name] => Miller
            [wage] => 100
            [children] => Array
                (
                    [0] => John
                    [1] => Kate
                )

        )

    [1] => Array
        (
            [year] => 1983
            [name] => Smith
            [wage] => 200
        )

    [2] => Array
        (
            [year] => 1980
            [name] => Mayer
            [wage] => 200
            [children] => Array
                (
                    [0] => Tom
                )

        )

    [3] => Array
        (
            [year] => 1981
            [name] => Mayer
            [wage] => 100
        )

    [4] => Array
        (
            [year] => 1980
            [name] => Clinton
            [wage] => 300
            [children] => Array
                (
                    [0] => Rosa
                    [1] => Dick
                    [2] => Christine
                )

        )

    [5] => Array
        (
            [year] => 1981
            [name] => Bush
            [wage] => 200
        )

)

Now comes the problem. I have no clue what additional information I get as I am not the master of the web service. I only know about the columns I need. In this case I only need "name" and "children". And I don't want to lose array elements just because they have no children.

So a returned array should look like this:

Array
(
    [0] => Array
        (
            [name] => Miller
            [children] => Array
                (
                    [0] => John
                    [1] => Kate
                )

        )

    [1] => Array
        (
            [name] => Smith
        )

    [2] => Array
        (
            [name] => Mayer
            [children] => Array
                (
                    [0] => Tom
                )

        )

    [3] => Array
        (
            [name] => Mayer
        )

    [4] => Array
        (
            [name] => Clinton
            [children] => Array
                (
                    [0] => Rosa
                    [1] => Dick
                    [2] => Christine
                )

        )

    [5] => Array
        (
            [name] => Bush
        )

)

Hence the function should look something like this:

$small_array=function($big_array, array("name","children"));

With the second argument containing an array of keys/columns to keep.

Any idea?

Dipanwita Kundu · Accepted Answer · 2016-04-15 10:46:35Z

2

Try this:

    $big_array = array(
array("year" => 1979, "name" => "Miller",   "wage" => "100", "children"=>array("John", "Kate")),
array("year" => 1983, "name" => "Smith",  "wage" => "200"),
array("year" => 1980, "name" => "Mayer",  "wage" => "200", "children"=>array("Tom")),
array("year" => 1981, "name" => "Mayer",  "wage" => "100"),
array("year" => 1980, "name" => "Clinton", "wage" => "300", "children"=>array("Rosa", "Dick", "Christine")),
array("year" => 1981, "name" => "Bush", "wage" => "200"));

$reqField = array('name','children');
$a = optimizeArray($big_array,$reqField);
echo "<pre>";
       print_r($a);

function optimizeArray($big_array,$reqField)
{
    $retArr = array();
    foreach($big_array as $mk=>$arr)
    {
        foreach($arr as $k=>$v)
        {
            if(in_array($k,$reqField) && isset($arr[$k]))
            {
               $retArr[$mk][$k] = $v;
            }

        }

    }
    return $retArr;
}

edited Apr 15, 2016 at 10:46

answered Apr 15, 2016 at 10:26

Dipanwita Kundu

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1 Comment

RJParikh Over a year ago

correct but user need function so you need to convert your code with function.

Sougata Bose · Accepted Answer · 2016-04-15 10:22:19Z

1

You can try this function -

$small_array = factor_array($big_array, array("name","children"));


/*
$main the big array
$keys the indexes to be extracted 
*/
function factor_array($main, $keys) {
    $temp = array();
    //loop through the big array
    foreach($main as $index => $array) {
        // loop through the keys array
        foreach($keys as $key) {
            if(isset($array[$key])) {// check if the key is set
                $temp[$index][$key] = $array[$key]; // store with the key
            }
        }

    }
    return $temp;
};

Fiddle

answered Apr 15, 2016 at 10:22

Sougata Bose

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Comments

Juergen Schulze · Accepted Answer · 2016-04-15 13:03:32Z

Ok, both answers are correct for my question. I want to thank you both. But after testing it I realized that there are even deeper array elements. So I guess we need an iterating, recursive solution which is far beyond my knowledge.

I got

$big_array = array(
array("year" => 1979, "name" => "Miller",   "wage" => "100", "children"=>array("John", "Kate")),
array("year" => 1983, "name" => "Smith",  "wage" => "200"),
array("year" => 1980, "name" => "Mayer",  "wage" => "200", "children"=>array("Tom")),
array("year" => 1981, "name" => "Mayer",  "wage" => "100"),
array("year" => 1980, "name" => "Clinton", "wage" => "300", "children"=>array("Rosa"=>array("Pet"=>array("Clover")), "Dick", "Christine")),
array("year" => 1981, "name" => "Bush", "wage" => "200"));
print_r($big_array);

Giving me

Array
(
    [0] => Array
        (
            [name] => Miller
            [children] => Array
                (
                    [0] => John
                    [1] => Kate
                )

        )

    [1] => Array
        (
            [name] => Smith
        )

    [2] => Array
        (
            [name] => Mayer
            [children] => Array
                (
                    [0] => Tom
                )

        )

    [3] => Array
        (
            [name] => Mayer
        )

    [4] => Array
        (
            [name] => Clinton
            [children] => Array
                (
                    [Rosa] => Array
                        (
                            [Pet] => Array
                                (
                                    [0] => Clover
                                )

                        )

                    [0] => Dick
                    [1] => Christine
                )

        )

    [5] => Array
        (
            [name] => Bush
        )

)

How can I optimize even multidimensional arrays?

deceze · Accepted Answer · 2016-04-15 13:08:09Z

0

It's a pretty trivial operation: use array_intersect_key to reduce a single array to only the keys specified, then do this for all arrays in your array:

$reduced = array_map(function (array $data) {
    return array_intersect_key($data, array_flip(['name', 'children']));
}, $originalArray);

answered Apr 15, 2016 at 13:08

deceze♦

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