Question

I would like to split an array:

$o = json_decode('[{"id":"1","color":"green"},{"id":"2","color":"green"},{"id":"3","color":"yellow"},{"id":"4","color":"green"}]');

based on the color attribute of each item, and fill corresponding sub arrays

$a = array("green", "yellow", "blue");

function isGreen($var){
    return($var->color == "green");
}

$greens = array_filter($o, "isGreen");
$yellows = array_filter($o, "isYellow");
// and all possible categories in $a..

my $a has a length > 20, and could increase more, so I need a general way instead of writing functions by hand

There doesn’t seem to exist a function array_split to generate all filtered arrays
or else I need a sort of lambda function maybe

Answer 1

You could do something like:

$o = json_decode('[{"id":"1","color":"green"},{"id":"2","color":"green"},{"id":"3","color":"yellow"},{"id":"4","color":"green"}]');

$greens = array_filter($o, function($item) {
    if ($item->color == 'green') {
        return true;
    }

    return false;
});

Or if you want to create something really generic you could do something like the following:

function filterArray($array, $type, $value)
{
    $result = array();
    foreach($array as $item) {
        if ($item->{$type} == $value) {
            $result[] = $item;
        }
    }

    return $result;
}

$o = json_decode('[{"id":"1","color":"green"},{"id":"2","color":"green"},{"id":"3","color":"yellow"},{"id":"4","color":"green"}]');
$greens = filterArray($o, 'color', 'green');
$yellows = filterArray($o, 'color', 'yellow');

In my second example you could just pass the array and tell the function what to filter (e.g. color or some other future property) on based on what value.

Note that I have not done any error checking whether properties really exist