带有foreach循环的PHP array_merge_recursive

How do you merge a loop of arrays into a single array(maybe object) adding each value to its associated common key?

Categories: 

Array ( [category] => introduction [timeZone] => Europe/Stockholm [language] => Danish )

Array ( [category] => introduction [timeZone] => Europe/Stockholm [language] => Danish )

Array ( [category] => e-learning [timeZone] => Europe/Stockholm [language] => German )

into

Collection

Array ( 
        [category] => Array (e-learning,introduction) 
        [timeZone] => Europe/Stockholm 
        [language] => Array (Danish,German)
)

Mycode so far:

foreach ($categories as $category){
   $collection = array_merge_recursive($category);
}

It seem like array_merge_recursive would achieve my result if I had $array1,$array2 sepcified within the PHP. But I need to do from a foreach loop.

Thanks.

Given the initial array named $categories, Consider:

$collection = array_merge_recursive(...$categories);
foreach($collection as &$item) $item = array_unique($item);

Output:

[
  'category' => ['intro','learning'],
  'timezone' => ['Europe'],
  'language' => ['Danish','German'],
]

Live demo

I suppose this tricky solution:

$collection = [];
// get keys of a first element of categories
$keys = array_keys($categories[0]);
// iterate over these keys
foreach ($keys as $key) {
    // use `array_unique` to eliminate duplicates
    $collection[] = array_unique(
        // `array_column` will give you all values under `$key`
        array_column($categories, $key)
    );
}

Of course this works since php5.5, as in this version we have array_column.