php arrays multidimensional-array codeigniter-2

How can manage multidimensional array in foreach() for tree view while multidimensional array form of multi level

I have this tree view of my nested array:

The Tree view

My questions:

I need to remove empty subarrays from this array, but array_filter() does not do this in a nested array. How can I achieve this?
What is the right way to use a multidimensional array in my case?
How to use a nested foreach() when I have a multidimensional array?

I have the following code:

foreach($legs as $element => $child_2){ 
    $result .= "{'name': '".$child_2['fullname']."', 'title': '".$child_2['gcn_id']."',";
    $result .= "'children': [";
    foreach($child_2 as $element_1 => $child_3){
        $result .="{'name': '".$child_3."', 'title': '".$child_3."',";
        $result .= "'children': [";
        foreach($child_3 as $element_2 => $child_4){
            $result.= "{ 'name': '".$child_4."', 'title': '".$child_4."' ,";
            $result .= "'children': [";
            /* foreach($child_4 as $k3=>$v3){
                #array_filter($v3);
                $result .= "{'name': '".$v3['fullname']."', 'title': '".$v3['gcn_id']."'},"; 

                }
            */
            $result .= "]},";
        }
        $result .= "]},";
    }
    $result .= "]";
    $result .= "},";
}

I have the following array:

multidimensional array

The desired output for the above input would start like this:

{ 
    "children": [{
        "name": "Wendy-Lynn Barr", 
        "title": "11312", 
        "children": [{
            "name": "Pauline Blake", 
            "title": "11303", 
            "children":[{
                "name":"Pauline Blake",
                "title":"11312",
            }]
        }]
    },{
        "title": "5064", 
        "name": "Ed Kilgour", 
        "referral_id": "5063", 
        'children': [{ 
            'name': 'Glen Starr', 
            'title': '6239' 
        },{ 
            'name': 'Allen Taylor',
            'title': '5155'
        },{ 
            'name': 'Roger Grosser', 
            'title': '5078'
        },{
            'name': 'Rodney Licari',
            'title': '5310'
        },{
            'name': 'Craig Corbitt',
            'title':'11302'
        },{ 
            'name': 'James Yates', 
            'title': '5097'
        }]
    }, 
    { /* ...etc */ },
    ]
}

Solution

Indeed array_filter does not work recursively.

Here is a recursive function that does the job of taking out null values:

function array_filter_recursive($arr, $cb = null) {
    if (empty($cb)) {
        $cb = function ($el) {
            return $el;
        };
    }
    $result = [];
    foreach($arr as $key => $val) {
        if (is_array($val)) $val = array_filter_recursive($val, $cb);
        if ($cb($val)) $result[$key] = $val;
    }
    return $result;
}

In general you need recursion (a function that calls itself) to solve problems involving arbitrary deeply nested arrays.

Now to your actual desired output (which I transferred from your comments into your question): that looks like JSON, for which you can use json_encode. There should never be a reason to build such a string yourself.

So you should never write something like this:

$result.= "{ 'name': '".$child_4."', 'title': '".$child_4."' ,";

For generating the specific output you are looking for, you could use this function:

function convert($arr) {
    $result = [];
    $byId = [];

    function recurse(&$result, &$byId, $arr) {
        if (!is_array($arr)) return;
        if (isset($arr["gcn_id"])) {
            $parent = $arr["referral_id"];
            $record = [
                "name" => $arr["fullname"],
                "title" => $arr["gcn_id"]
            ];
            $byId[$arr["gcn_id"]] = &$record; 
            if (isset($byId[$parent])) {
                $byId[$parent]["children"][] = &$record;
            } else {
                $result[] = &$record;
            }
        } else {
            foreach($arr as $child) {
                recurse($result, $byId, $child);
            }
        }
    }

    recurse($result, $byId, $arr);    
    return $result;
}

$result = json_encode(convert($legs), JSON_PRETTY_PRINT);

echo $result;

See it run on eval.in. It produces this output:

[
    {
        "name": "Wendy-Lynn Barr",
        "title": 11312,
        "children": [
            {
                "name": "Pauline Blake",
                "title": 11303
            }
        ]
    },
    {
        "name": "Ed Kilgour",
        "title": 5064,
        "children": [
            {
                "name": "Craig Corbitt",
                "title": 11302,
                "children": [
                    {
                        "name": "Kristi  Iles",
                        "title": 5175,
                        "children": [
                            {
                                "name": "Joshua  Iles",
                                "title": 6013
                            }
                        ]
                    },
                    {
                        "name": "Chris Chowning",
                        "title": 6308,
                        "children": [
                                // ...etc

The key here is not only recursion, but also referencing a record by its ID (title). This referencing can be done with the & symbol, both in function parameters and in assignments.