recursive function : filtering large multidimensional array by key element to HTML list

Question

I have a multidimensional array as a result from a webservice called from PHP. I cannot edit the webservice, but the result is as

array (size=5)
 'id' => int 0
 'name' => 
 array (size=7)
 'it' => string 'Tutti' (length=5)
 'ca' => string 'Tots' (length=4)
 'es' => string 'Todos' (length=5)
 'de' => string 'Alle' (length=4)
 'fr' => string 'Tous' (length=4)
 'nl' => string 'Alle' (length=4)
 'en' => string 'All' (length=3)
 'tree' => 
 array (size=0)
 empty
 'languages' => 
 array (size=7)
 'subTypes' => 
 array (size=4)
 0 => 
 array (size=5)
 'id' => int 1
 'name' => 
 array (size=29)
 ...
 'tree' => 
 array (size=1)
 ...
 'languages' => 
 array (size=29)
 ...
 'subTypes' => 
 array (size=3)
 ...
 1 => 
 array (size=5)
 'id' => int 2
 'name' => 
 array (size=29)
 ...
 'tree' => 
 array (size=1)
 ...
 'languages' => 
 array (size=29)
 ...
 'subTypes' => 
 array (size=6)
 ...

As you can see, you can interpret it as a multidimensional array of objects. Each objects can have child objects of same type.

My goal is to get only the elements on a specific language, fe en (and thus rest is not taken). I thought to use a recursive function.

// filter array
function getByKey($array, $search, $level, $valuesUsed) {
 echo '<ul>';
 foreach($array as $key => $value) {
 if(is_array($array[$key])) {
 $valuesUsed = getByKey($array[$key], $search, $level + 1, $valuesUsed);
 } else if ($key === $search) {
 if(!in_array($value, $valuesUsed)) {
 echo "<li> $key = $value </li>";
 $valuesUsed[] = $value;
 }
 }
 }
 echo '</ul>';
 return $valuesUsed;
}

Then I call the above function from my HTML template by

<div id="foo">
 <?php
 getByKey($routeTypes, 'en', 0, array());
 ?>
</div>

$routeTypes is the array, obtained from the webservice. It works as expected, it results as the list here below, which I can wrap with a js library.

<ul>
 <li>this is level1</li>
 <li>this is level1</li>
 <li>
 <ul>
 <li>this is level 2</li>
 <li>this is level 2</li>
 <li>
 ... level++
 </li>
 </ul>
 </li>
</ul>

Now, I'm questioning myself if this can be improved ? It doesn't take long to have a list from a large multidimensional array. (a simple print_r command resulted in 45000+ characters).

Especially checking the $valuesUsed array, to prevent duplicates (yes the webservice has objects which contains child keys which is similar to level - 2 parent (or on other level ...... ))

Each time I am running through the lower levels, I am looping through the $valuesUsed array. Is there not a better way to loop through the sublevels ? Maybe an array_walk() or array_walk_recursive() with a callback function ?

• Marc-Andre: Is this complete code ? It's seems to be missing some part ? Does it work on it's own ? Are you here for a review or something else ?
• KarelG: yes, i'm here for a review. Just asking if the recursive function can be improved. The above function will be called in the HTML template. (it displays the list of which i want on the webpage). Edited my post.
• Marc-Andre: I was asking to come up with a title. The title of your question should describe what your code do!

Answer 1

You can choose a (key => value) pair recursively with this function:

function array_value_recursive($key, array $arr){
 $val = array();
 array_walk_recursive($arr, function($v, $k) use($key, &$val){
 if($k == $key) array_push($val, $v);
 });
 return count($val) > 1 ? $val : array_pop($val);
}

This function makes use of array_walk_recursive() to push into a placeholder array whatever value is pointed to by whichever key matches our needle key.

Proof code:

$array = array(
 'id' => 0,
 'name' => array(
 'it' => 'Tutti',
 'ca' => 'Tots',
 'es' => 'Todos', 
 'de' => 'Alle' ,
 'fr' => 'Tous',
 'nl' => 'Alle',
 'en' => 'All'
 ),
 'languages' => array(
 "d" => 33
 ),
 'subTypes' => array(
 0 => array(
 'id' => 1,
 'name' => array(
 'it' => 'Tutti',
 'ca' => 'Tots',
 'es' => 'Todos', 
 'de' => 'Alle' ,
 'fr' => 'Tous',
 'nl' => 'Alle',
 'en' => 'All'
 )
 ),
 1 => array(
 'id' => 1,
 'name' => array(
 'it' => 'Tutti',
 'ca' => 'Tots',
 'es' => 'Todos', 
 'de' => 'Alle' ,
 'fr' => 'Tous',
 'nl' => 'Alle',
 'en' => 'All'
 )
 ),
 2 => array(
 'id' => 1,
 'name' => array(
 'it' => 'Tutti',
 'ca' => 'Tots',
 'es' => 'Todos', 
 'de' => 'Alle' ,
 'fr' => 'Tous',
 'nl' => 'Alle',
 'en' => 'All'
 )
 )
 )
);
print_r(array_value_recursive("de", $array));

The above test code, which seeks all "de" keys, will output:

Array ( 
 [0] => Alle 
 [1] => Alle 
 [2] => Alle 
 [3] => Alle
)

• KarelG: thanks for your suggestion, but yours code didn't kept the child level of the main array. The goal is to get a nested list (menu - submenu) as mentioned in my post.