How to unset (remove) a collection element after fetching it?

I have a collection which I want to iterate and modify while I fetch some of its elements. But I could't find a way or method to remove that fetched element.

$selected = []; 
foreach ($collection as $key => $value) {
      if ($collection->selected == true) {
          $selected[] = $value;
          unset($value);
      }
}

This is just a representation of my question for demonstration.

After @Ohgodwhy advice the forget() function I checked it again and saw that I actually misunderstood the function. It was exactly as I was looking for.

So for working solution I have added $collection->forget($key) inside the if statement.

Below is the working solution of my problem, using @Ohgodwhy's solution:

$selected = []; 
foreach ($collection as $key => $value) {
      if ($collection->selected == true) {
          $selected[] = $value;
          $collection->forget($key);
      }
}

(this is just a demonstration)

You would want to use ->forget()

$collection->forget($key);

Link to the forget method documentation

Or you can use reject method

$newColection = $collection->reject(function($element) {
    return $item->selected != true;
});

or pull method

$selected = []; 
foreach ($collection as $key => $item) {
      if ($item->selected == true) {
          $selected[] = $collection->pull($key);
      }
}

Laravel Collection implements the PHP ArrayAccess interface (which is why using foreach is possible in the first place).

If you have the key already you can just use PHP unset.

I prefer this, because it clearly modifies the collection in place, and is easy to remember.

foreach ($collection as $key => $value) {
    unset($collection[$key]);
}

I'm not fine with solutions that iterates over a collection and inside the loop manipulating the content of even that collection. This can result in unexpected behaviour.

See also here: https://stackoverflow.com/a/2304578/655224 and in a comment the given link http://php.net/manual/en/control-structures.foreach.php#88578

So, when using foreach it seems to be ok but IMHO the much more readable and simple solution is to filter your collection to a new one.

/**
 * Filter all `selected` items
 *
 * @link https://laravel.com/docs/7.x/collections#method-filter
 */
$selected = $collection->filter(function($value, $key) {
    return $value->selected;
})->toArray();

> If you know the key which you unset then put directly by comma > separated

unset($attr['placeholder'], $attr['autocomplete']);

You can use methods of Collection like pull, forget, reject etc.

But every Collection method returns an entirely new Collection instance.

Doc link: https://laravel.com/docs/8.x/collections#introduction