How to sort all levels of multidimensional array by key?

Question

I found this code for sorting:

usort($array, function($a, $b) {
    return $a['order_inside_level'] - $b['order_inside_level'];
});

It's good for one level. I have something like that:

array(
 array(
     'level'=>'aaa',
     'order'='1',
     'subs'=>array(
         array(
             'level'=>'bbb',
             'order'='1',
             'subs'=>array(
                 array(
                     'level'=>'ccc',
                     'order'='1',
                     'subs'=>array(
                         array(
                             'level'=>'ddd',
                             'order'='1',
                             'subs'=>array(
                                 ...
                             )
                         )
                     )
                 )
                 ,
                 array(
                     'level'=>'ccc',
                     'order'='2',
                     'subs'=>array(

                     )
                 )
             ),
         array(
             'level'=>'bbb',
             'order'='2'
         ),
         array(
             'level'=>'bbb',
             'order'='3'
         )
         )
     )
 ),
 array(
     'level'=>'aaa',
     'order'='2',
     'subs'=>array(

     )
 )

 )

Array may have any depth and any number of elements in each level. I need to sort each level of depth (aaa,bbb,ccc, etc) using the code above by key 'order'.

I am writing menu generator. Menu generates from such array. And order in each level is important. — John Smith
– John Smith, Commented Aug 7, 2014 at 21:27

Luke Willis · Accepted Answer · 2014-08-07 21:52:36Z

1

You will need to do this recursively.

recursive_sort($arr, $func) {
    foreach ($arr as $key => $val) {
        if (is_array($val)) {
            recursive_sort($val, $func);
        }
    }
    usort($arr, $func);
}

This code will iterate over the given array, and for each value that is an array, call itself with the value. The result is that usort will be called for every array within the structure.

You would call the function the same as you would usort:

recursive_sort($array, function($a, $b) {
    return $a['order_inside_level'] - $b['order_inside_level'];
});

edited Aug 7, 2014 at 21:52

answered Aug 7, 2014 at 21:46

Luke Willis

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4 Comments

John Smith Over a year ago

There are arrays of arrays [array(0=>array(),1=>array(),...)] in my example. They are arrays. It means they will be sorted by 'order', but they have no key 'order' (they are not associative arrays, they just have numeric indexes) Maby that is the reason of 'illegal string offset'?..

John Smith Over a year ago

I cant make usort work inside of function: function fs($array){ return usort($array, 'sortByOrder');}; fs($myarray); - doesn't work. Without function it works: usort($myarray, 'sortByOrder'); How is that possible?..

John Smith Over a year ago

sandbox.onlinephpfunctions.com/code/… - here is example. Usort doesn't work inside function. It works outside function (uncomment 95 string). So that your code doesn't work too...

John Smith Over a year ago

I've decided the problem about work inside of function. Now sorting happens only in the first level of array - sandbox.onlinephpfunctions.com/code/…

John Smith · Accepted Answer · 2014-08-08 10:35:11Z

1

function recursive_sort(&$arr) {
            fs($arr);
        foreach($arr as $k=> &$v){
            if (isset($v['subs'])) {
                 recursive_sort($v['subs']);
             }
        }
}


function sortByOrder($a, $b) {
    return $a['order_inside_level'] - $b['order_inside_level'];
}

function fs(&$array){

    usort($array, 'sortByOrder');

}

After multiple tries I have this. It works. Name of key (subs) is hardcoded what is not so good, but... I am glad it works.

answered Aug 8, 2014 at 10:35

John Smith

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