Looping through level 2 of multidimensional array

Question

So I have an array like so :

$arr = array(
  "element1"  => array("group" => "g1", "other_stuff" => "foo"),
  "element2"  => array("group" => "g1", "other_stuff" => "bar"),
  "element3"  => array("group" => "g1", "other_stuff" => "foo"),
  "element4"  => array("group" => "g2", "other_stuff" => "bar"),
  "element5"  => array("group" => "g2", "other_stuff" => "foo"),
  "element6"  => array("group" => "g2", "other_stuff" => "bar"),
  "element7"  => array("group" => "g3", "other_stuff" => "foo"),
  "element8"  => array("group" => "g3", "other_stuff" => "bar"),
  "element9"  => array("group" => "g3", "other_stuff" => "foo"),
);

I'd like to display the elements in a shuffled order within each group, preceded by the group, the order of the groups being shuffled too. So for instance :

g2
-> element5
-> element4
-> element6
g3
-> element7 
-> element9
-> element8
g1
-> element2 
-> element3
-> element1

I thought I could do something along this line :

shuffle($arr);

foreach($arr[]["group"] as $current_group){
    echo "$current_group"
    foreach($arr[][$current_group] as $current_element){
        echo "-> ".$ current_element."<br />"
    }
}

But no, $arr[]["group"] isn't valid. How can I achieve that ?

Thanks

(It's 2AM where I am so my pseudo code might be uber broken, sorry, I just want to convey the idea I was following)

Kevin · Accepted Answer · 2016-12-08 01:39:38Z

3

Just group them first using the group value. Use that as a key in a new container assignment:

$final_arr = array();
foreach($arr as $key => $a) {
    $final_arr[$a['group']][] = $key;
}

This should yield the following structure:

Array
(
    [g1] => Array
        (
            [0] => element1
            [1] => element2
            [2] => element3
        )

    [g2] => Array
        (
            [0] => element4
            [1] => element5
            [2] => element6
        )

    [g3] => Array
        (
            [0] => element7
            [1] => element8
            [2] => element9
        )

)

Now its up to you how you'll present it (via just simple -> string or with HTML).

Dirty example:

echo '<ul>';
foreach($final_arr as $group => $f) {
    echo '<li>', $group;
    echo '<ul>'; foreach($f as $e) { echo "<li>{$e}</li>"; } echo '</ul>';
    echo '</li>';

}
echo '</ul>';

If you want that shuffle preserved, just get the keys shuffle it and transfer it:

$keys = array_keys($arr); // get the keys of the original
shuffle($keys); shuffle the keys
$new_arr = array(); // initialize a temp container
foreach($keys as $k) {
    $new_arr[$k] = $arr[$k]; // match the shuffled key and assign it
}
$arr = $new_arr; // overwrite

edited Dec 8, 2016 at 1:39

answered Dec 8, 2016 at 1:08

Kevin

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2 Comments

François M. Over a year ago

Thanks. It works without shuffle($arr); but it doesn't with it.

Kevin Over a year ago

@fmalaussena shuffle eliminates the keys, that's why it doesn't work when coupled with it

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