Default array values if key doesn't exist?

Question

If I have an array full of information, is there any way I can a default for values to be returned if the key doesn't exist?

function items() {
    return array(
        'one' => array(
              'a' => 1,
              'b' => 2,
              'c' => 3,
              'd' => 4,
         ),
         'two' => array(
              'a' => 1,
              'b' => 2,
              'c' => 3,
              'd' => 4,
         ),
         'three' => array(
              'a' => 1,
              'b' => 2,
              'c' => 3,
              'd' => 4,
         ),
    );
}

And in my code

$items = items();
echo $items['one']['a']; // 1

But can I have a default value to be returned if I give a key that doesn't exist like,

$items = items();
echo $items['four']['a']; // DOESN'T EXIST RETURN DEFAULT OF 99

Answer 1

In PHP7, as Slavik mentioned, you can use the null coalescing operator: ??

Link to the PHP docs.

Answer 2

You can use DefaultArray from Non-standard PHP library. You can create new DefaultArray from your items:

use function \nspl\ds\defaultarray;
$items = defaultarray(function() { return defaultarray(99); }, $items);

Or return DefaultArray from the items() function:

function items() {
    return defaultarray(function() { return defaultarray(99); }, array(
        'one' => array(
              'a' => 1,
              'b' => 2,
              'c' => 3,
              'd' => 4,
         ),
         'two' => array(
              'a' => 1,
              'b' => 2,
              'c' => 3,
              'd' => 4,
         ),
         'three' => array(
              'a' => 1,
              'b' => 2,
              'c' => 3,
              'd' => 4,
         ),
    ));
}

Note that we create nested default array with an anonymous function function() { return defaultarray(99); }. Otherwise, the same instance of default array object will be shared across all parent array fields.

Answer 3

Use Array_Fill() function

http://php.net/manual/en/function.array-fill.php

$default = array(
              'a' => 1,
              'b' => 2,
              'c' => 3,
              'd' => 4,
         );
$arr = Array_Fill(1,3,$default);
print_r($arr);

This is the result:

Array
(
    [1] => Array
        (
            [a] => 1
            [b] => 2
            [c] => 3
            [d] => 4
        )

    [2] => Array
        (
            [a] => 1
            [b] => 2
            [c] => 3
            [d] => 4
        )

    [3] => Array
        (
            [a] => 1
            [b] => 2
            [c] => 3
            [d] => 4
        )

)

Answer 4

I know this is an old question, but my Google search for "php array default values" took me here, and I thought I would post the solution I was looking for, chances are it might help someone else.

I wanted an array with default option values that could be overridden by custom values. I ended up using array_merge.

Example:

<?php
    $defaultOptions = array("color" => "red", "size" => 5, "text" => "Default text");
    $customOptions = array("color" => "blue", "text" => "Custom text");
    $options = array_merge($defaultOptions, $customOptions);
    print_r($options);
?>

Outputs:

Array
(
    [color] => blue
    [size] => 5
    [text] => Custom text
)

Answer 5

This should do the trick:

$value =  isset($items['four']['a']) ? $items['four']['a'] : 99;

A helper function would be useful, if you have to write these a lot:

function arr_get($array, $key, $default = null){
    return isset($array[$key]) ? $array[$key] : $default;
}

Answer 6

You could also do this:

$value =  $items['four']['a'] ?: 99;

This equates to:

$value =  $items['four']['a'] ? $items['four']['a'] : 99;

It saves the need to wrap the whole statement into a function!

Note that this does not return 99 if and only if the key 'a' is not set in items['four']. Instead, it returns 99 if and only if the value $items['four']['a'] is false (either unset or a false value like 0).