Checking for existing key in multi-dimensional array

Question

Say I have a data structure like this:

array(3) {
  ["id"]=>
  int(1)
  ["name"]=>
  string(3) "foo"
  ["message"]=>
  array(1) {
    ["action"]=>
    string(3) "PUT"
  }
}

Where 'message' and 'action' are both optional. To check if they're present my first attempt would be to write something like this:

if (array_key_exists('message', $array) && array_key_exists('action', $array['message'])){
}

Is there a cleaner implementation?

Answer 1

No, this is just the way of doing it.

Even when I'm not limited to a certain script language, I can't think of an cleaner solution?

Answer 2

You can just do this!

if (isset($array["message"]["action"])) { /*...*/ }

Proof:

<?php

error_reporting(E_ALL);
ini_set('error_reporting', E_ALL);
ini_set('display_errors', 1);

$array = [
    "id" => 1,
    "name" => "foo",
    "message" => [
        "action" => "PUT",
    ],
];

var_dump(isset($array["message"]["action"])); // true


$array = [
    "id" => 1,
    "name" => "foo"
];

var_dump(isset($array["message"]["action"])); // false

No log entries.

Do note that if your value is null, then isset will also return false. You probably shouldn't be creating values with null.

Answer 3

Not clearer but probably the fastest solution:

if ((isset($array["message"]["action"]) ||
        (array_key_exists('message', $array) && array_key_exists('action', $array['message']))) {
    /* ... */
}

The second check is needed because some values evaluated with isset() will result false despite the index does exist.

Answer 4

I'm using this in a project of mine, but I'm using null as a muted state. (php 5.6)

<?php

function &option_select($options, $default, ...$path) {
    if(!isset($path[0])) { return $options; }
    $cursor = &$options;
    foreach($path as $key) {
        if(isset($cursor[$key])) { $cursor = &$cursor[$key]; } else { return $default; }
    } return $cursor;
}

It's a function that will lookup a path in a tree.

echo option_select([A=>[B=>[C=>'hello world']]], 'NO?', 'A', 'B', 'C');

As you can see. I'm looping over the values over a array: path. In the beginning I'm setting a cursor as reference to a array I have to search in. Every time I find a new key, I'm setting the reference of the cursor to the current key I'm searching for. If you have xdebug and a good GUI, you can rewrite it to the algorithm you want. It's the isset($cursor[$key]) you have to change. Or inject it as a function: f($cursor, $key, $default) => (bool)

Answer 5

Been looking for a similar solution myself and came up with this. Works to determine if the key is set at all - and will return TRUE even if the value of the "action" key is NULL.

if (isset($array['message']) && array_key_exists('action',$array['message'])) {
    /* ... */
}

If $array['message'] has no keys, the isset will return FALSE stopping the IF statement. If $array['message'] has any keys - even ones with NULL values - isset will return TRUE, allowing you to safely check if the 'action' array key exists in $array['message'].