Array defaults if key does not exist?

Question

If I have an array full of information, can I return values ​​by default if the key does not 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 that will be returned if I give a key that does not 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 on “php array defaults” took me here and I thought that posting the solution I was looking for would likely help someone else.

I need an array with default values ​​that can be overridden by user 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

Starting with PHP 7, there is a new operator specifically designed for these cases called the Null Coalesce Operator .

So now you can do:

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

instead

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

There is another way to do this before PHP 7:

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

And the following will work without problems:

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

But note that when using this method, calling an array property for a value that is not an array will throw an error. for example

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

In addition, there is a case when a fatal error will be issued:

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

In the end, there is an unpleasant workaround, but it works almost well (in some cases, the problems described below occur):

 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 

Answer 3

This should do the trick:

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

A helper function would be useful if you need to write a lot:

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

Answer 4

You can also do this:

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

It means:

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

This eliminates the need to bind the entire instruction to a function!

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

Answer 5

Not that I knew.

You will need to check isset separately

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

Answer 6

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 7

The question is very old, but maybe my solution is still useful. For projects where I very often need "if array_key_exists", for example, to parse Json, I developed the following function:

 function getArrayVal($arr, $path=null, $default=null) { if(is_null($path)) return $arr; $t=&$arr; foreach(explode('/', trim($path,'/')) As $p) { if(!array_key_exists($p,$t)) return $default; $t=&$t[$p]; } return $t; } 

Then you can simply “query” the array as:

 $res = getArrayVal($myArray,'companies/128/address/street'); 

This is easier to read than the equivalent old-fashioned way ...

 $res = (isset($myArray['companies'][128]['address']['street']) ? $myArray['companies'][128]['address']['street'] : null); 

Answer 8

I don’t know how to do this exactly with the code that you specified, but you can bypass it using a function that takes any number of arguments and returns the desired parameter or default value.

Using:

 echo arr_value($items, 'four', 'a'); 

or

 echo arr_value($items, 'four', 'a', '1', '5'); 

Functions:

 function arr_value($arr, $dimension1, $dimension2, ...) { $default_value = 99; if (func_num_args() > 1) { $output = $arr; $args = func_gets_args(); for($i = 1; $i < func_num_args(); $i++) { $outout = isset($output[$args[$i]]) ? $output[$args[$i]] : $default_value; } } else { return $default_value; } return $output; } 

Answer 9

You can use DefaultArray from the PHP Custom Library . You can create a new ItemArray from your elements:

 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 a default nested array with the anonymous function function() { return defaultarray(99); } function() { return defaultarray(99); } . Otherwise, the same instance of the array object will be used by default for all fields of the parent array.

Answer 10

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

Link to PHP Docs .

Answer 11

I think there is a better answer: is there a better way for PHP to get the default value of a key from an array (dictionary)?

i think i could be defined as a duplicate