Extracting only specific array elements

[NotionCommotion]

Recommendations on the best way to extract only specific elements from an array?  What about the following?  Thanks

        while($source=$stmt->fetch(\PDO::FETCH_ASSOC)) {
            if($source['guid']) {
                $clients[]=array_intersect_key($source, ['name'=>null,'guid'=>null]);
            }
            else {
                $servers[]=array_intersect_key($source, ['name'=>null,'ip'=>null,'port'=>null,'encrypt_key'=>null]);
            }
        }

[requinix]

I'd either do that or the obvious solution, mostly depending on whether I remembered about array_intersect_key at the time.

[Barand]

or simply

$clients[] = [ 'name' => $source['name'], 'guid' = $source['guid'] ];

[EDIT] Requinix's turn to beat me to the post

Edited October 24, 2016 by Barand

[NotionCommotion]

I'd either do that or the obvious solution, mostly depending on whether I remembered about array_intersect_key at the time.

 

Obvious being $clients[]=['name'=>$source['name'],'guid'=>$source['guid']]; with maybe some isset checks?

[NotionCommotion]

 

or simply

$clients[] = [ 'name' => $source['name'], 'guid' = $source['guid'] ];

 

You beat me by 1 second!

 

Would you recommend doing it your way if there are only a couple of elements, but using array_intersect_key() if there are more than say 5?

[Barand]

Possibly, it is a neat solution for those who understand the function. Another option may be to organize your query so you can use array_slice().

Edited October 24, 2016 by Barand

[requinix]

but using array_intersect_key() if there are more than say 5?

You aren't really saving yourself much: still typing out the basic key => value stuff for each element you want.

 

A sort of "array_choose" function would be nice to have built-into PHP. I wouldn't implement it in userland just for this one purpose, though.

/**
 * Extract a subset of an array
 *
 * @param array $array Source array
 * @param array|scalar $key An array of keys, or the first key
 * @param scalar ... Additional keys if $key is not an array
 * @return array
 */
function array_choose(array $array, ...$keys) {
	$return = array();
	foreach (isset($keys[0]) && is_array($keys[0]) ? $keys[0] : $keys as $key) {
		if (array_key_exists($array, $key)) {
			$return[$key] = $array[$key];
		}
	}
	return $return;
}

Edited October 24, 2016 by requinix
switching out isset for array_key_exists

[kicken]

You could use array_fill_keys to build the second parameter to array_intersect_key easier for larger arrays.

 

if($source['guid']) {
    $clients[]=array_intersect_key($source, array_fill_keys(['name','guid'], null));
}
else {
    $servers[]=array_intersect_key($source, array_fill_keys(['name','ip','port','encrypt_key'], null));
}

[NotionCommotion]

You could use array_fill_keys to build the second parameter to array_intersect_key easier for larger arrays.

 

Or array_flip()