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

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 2

As of PHP 7, there is a new operator specifically designed for these cases, called Null Coalesce Operator.

So now you can do:

echo $items['four']['a'] ?? 99; 

instead of

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

There is another way to do this prior the PHP 7:

function get(&$value, $default = null) {     return isset($value) ? $value : $default; } 

And the following will work without an issue:

echo get($item['four']['a'], 99); echo get($item['five'], ['a' => 1]); 

But note, that using this way, calling an array property on a non-array value, will throw an error. E.g.

echo get($item['one']['a']['b'], 99); // Throws: PHP warning:  Cannot use a scalar value as an array on line 1 

Also, there is a case where a fatal error will be thrown:

$a = "a"; echo get($a[0], "b"); // Throws: PHP Fatal error:  Only variables can be passed by reference 

At final, there is an ugly workaround, but works almost well (issues in some cases as described below):

function get($value, $default = null) {     return isset($value) ? $value : $default; } $a = [     'a' => 'b',     'b' => 2 ]; echo get(@$a['a'], 'c');      // prints 'c'  -- OK echo get(@$a['c'], 'd');      // prints 'd'  -- OK echo get(@$a['a'][0], 'c');   // prints 'b'  -- OK (but also maybe wrong - it depends) echo get(@$a['a'][1], 'c');   // prints NULL -- NOT OK echo get(@$a['a']['f'], 'c'); // prints 'b'  -- NOT OK echo get(@$a['c'], 'd');      // prints 'd'  -- OK echo get(@$a['c']['a'], 'd'); // prints 'd'  -- OK echo get(@$a['b'][0], 'c');   // prints 'c'  -- OK echo get(@$a['b']['f'], 'c'); // prints 'c'  -- OK echo get(@$b, 'c');           // prints 'c'  -- OK