Is there an "automatic-null" operator for undefined index on an array in PHP?

Question

I've been finding that I'm writing a lot of code like this:

$customData1 = $user['custom_data_1'] ?? null;
$customData2 = $user['custom_data_2'] ?? null;
$customData3 = $user['custom_data_3'] ?? null;

It seems like there should be some kind of simpler syntax for this.

I'd love for this to work without error:

$customData1 = $user['custom_data_1'];

And $customData1 would be null if the index is not defined. But this presents a PHP error. Is there something similar to this:

$customData1 = $user['custom_data_1']?;

I understand using ?? when the fallback is something less unusual, but null is quite common and I don't see why there isn't a default for this operator.

I know I could also do this:

$user = (object) $user;
$customData1 = $user->custom_data_1;
$customData2 = $user->custom_data_2;
$customData3 = $user->custom_data_3;

But this kind of goes beyond what I'm actually trying to find an answer for.

Does this answer your question? Using a function to initialise a variable if it not set - PHP — pavel
– pavel, Commented Nov 27, 2020 at 22:37
I am looking for built-in PHP functionality. I'm now thinking it doesn't exist. — D'Arcy Rail-Ip
– D'Arcy Rail-Ip, Commented Nov 27, 2020 at 22:48
At least, with ?? null, you're explicitly stating that you expect the index to not exist. Explicit code is always better. If PHP didn't throw a warning when a key didn't exist, then you could easily miss typos on keys, among other things. Now in most cases you're better off using objects/DTOs (very basic objects), so your properties would exist anyway and have a default value. — Jeto
– Jeto, Commented Nov 27, 2020 at 22:49
Note: you could do $customData1 = @$user['custom_data_1']; (which is pretty much what you're looking for). But, seriously, don't :) — Jeto
– Jeto, Commented Nov 27, 2020 at 23:09
@Jeto: no, it really isn't what he's looking for... Warnings will be still generated and page will be slower. Only one right approach is to solve warning, not to close eyes before them. — pavel
– pavel, Commented Nov 28, 2020 at 1:27

loydg · Accepted Answer · 2020-11-27 23:02:50Z

If you're still willing to consider involving objects, just not the one you mentioned, the you can implement the predefined interface ArrayAccess. Something like:

class stdArray implements ArrayAccess
{
    private $container = [];

    public function __const(array $array = [])
    {
        $this->container = $array;
    }

    ...

    public function offsetGet($offset)
    {
        return $this->container[$offset] ?? null;
    }

    ...

    // So we don't have to instantiate a new Object for each array if we don't need to.
    // Just me mindful though :P
    public function replace(array $array)
    {
        return $this->container = $array;
    }
}

For example:

$arr = new stdArray($user);
$customData1 = $user['custom_data_1'];
$customData2 = $user['custom_data_2'];
$customData3 = $user['custom_data_3'];

$arr = new stdArray();
foreach ($multiArray as $subArray) {
    $arr->replace($subArray);
    $customData1 = $arr['custom_data_1'];
    $customData2 = $arr['custom_data_2'];
    $customData3 = $arr['custom_data_3'];

    // Do some operations ...
}

Haven't actually tested this, but this might/should work.

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