array_mask, Seeking alternative code

Question

I would really love to hear your critiques on:

• Code quality
• Code clarity
• More efficient alternative code

Code:

function array_mask(array $source, array $filter){
 foreach ($source as $key => $value){
 if (!isset($filter[$key])){
 if (array_search($key, $filter) !== false){
 continue;
 }
 unset($source[$key]);
 } else {
 if (is_array($source[$key])){
 $source[$key] = array_mask($source[$key], $filter[$key]);
 }
 }
 }
 return $source;
} 
$source = array(
 'page' => array(
 'q' => 'alkflsdj',
 'x' => 1,
 9 => 'm'
 ),
 'news' => 7
);
$filter = array(
 'page' => array(
 9
 ),
 'news'
); 
$result = array_mask($source, $filter);
var_dump($result);

Result:

array
 'page' => 
 array
 9 => string 'm' (length=1)
 'news' => int 7

Answer 1

You can use built-in functions instead. Like this for example:

function array_mask(array $source, array $filter)
{
 $source = array_intersect_key($source, $filter);
 foreach ($source as $key => $value)
 if (is_array($value))
 $source[$key] = array_mask($source[$key], $filter[$key]);
 return $source;
}
$source = array(
 'page' => array(
 'q' => 'alkflsdj',
 'x' => 1,
 9 => 'm'
 ),
 'news' => 7
);
$filter = array(
 'page' => array(
 9 => ''
 ),
 'news' => ''
);
var_dump (array_mask($source, $filter));

• Fedor: I had this idea, but for some reason she didn't like. Now like normal.

Answer 2

Looks good to me, but you can make a small optimization:

change this

 if (array_search($key, $filter) !== false){
 continue;
 }
 unset($source[$key]);

to

 if (array_search($key, $filter) === false){
 unset($source[$key]);
 }

• Jeff Vanzella: Just a suggestion, you might want to explain why you are suggesting the change. Doing so will greatly increase the value of this answer.