Dynamically add empty index to array based on default indexes

I have below array, which includes a set of default indexes, that must be present in my final array:

'entities' => [
        'deliveredAt',
        'issuedAt',
        'totals' => [
            'due',
            'gross',
            'net',
            'tax' => [
                'amount',
                'net',
                'rate',
            ],
        ]
],

The above array is saved in a variable called $entities.

Now, I have a 3rd party API, that will return the above entities, but only include them in the response if the entity contains a value.

For example, a $response can look like this:

array:2 [▼
  "issuedAt" => "2020-08-20"
  "totals" => array:1 [▼
    "tax" => []
  ]
]

As you can see, if comparing the returned array with the indexes that I expect, there is a few missing:

• deliveredAt
• totals.due, totals.gross, totals.net, totals.tax.amount, totals.tax.net, totals.tax.rate

I am trying to make a method that can iterate over the $response array, and check if it contains the indexes that I expect. If not, I simply want to set the index with a value of null.

Below is what I have so far:

foreach ($entities as $key => $entity) {
         if (!is_array($entity)) {
             if (!isset($response[$entity])) {
                    $response[$entity] = null;
             }
         }
}

However, this will only add an index that is not an array. In this example, it will only add: deliveredAt => null.

How can I do, so the above method can iterate through multiple at least 2 nested arrays and add the index name and null value?

Answer

You can define initial array with keys and NULL (or whatever you need) as values:

$entities = [
    'deliveredAt' => null,
    'issuedAt' => null,
    'totals' => [
        'due' => null,
        'gross' => null,
        'net' => null,
        'tax' => [
            'amount' => null,
            'net' => null,
            'rate' => null,
        ],
    ]
];

// here's your real data
$realData = [
  "issuedAt" => "2020-08-20",
  "totals" => [
    "tax" => [
      'net' => 42,    
    ]
  ]
];
// now use array_replace_recursive to replace keys in `$entities` with values of `$realData`
print_r(array_replace_recursive($entities, $realData));

Fiddle.

Also note that keys from $realData that do not exist in $entities will be added to result.