Laravel 5 Collections: Converting a Multi-Dimensional Collection Into a Single Dimension With collapse

The collapse method combines all the first-level items of a collection into a new, single collection. The returned value of the collapse method is an instance of the Collection class.

#Signature

1public function collapse();

#Example Use

We will create a simple collection to work with like this:

 1use Illuminate\Support\Collection;
 2 
 3$first = [
 4    0, 1, 2, 3, 4
 5];
 6 
 7$second = [
 8    5, 6, 7, 8 , 9
 9];
10 
11$collection = new Collection([$first, $second]);

The $collection variable now has an internal structure similar to the following output:

 1object(Illuminate\Support\Collection)
 2  protected 'items' =>
 3    array
 4      0 =>
 5        array
 6          0 => int 0
 7          1 => int 1
 8          2 => int 2
 9          3 => int 3
10          4 => int 4
11      1 =>
12        array
13          0 => int 5
14          1 => int 6
15          2 => int 7
16          3 => int 8
17          4 => int 9

We can see that our collection contains two arrays. Using the collapse method, we can get a Collection instance that combines the two arrays above:

1$collapsed = $collection->collapse();

Now, the $collapsed variable would have a value similar to the following:

 1object(Illuminate\Support\Collection)
 2  protected 'items' =>
 3    array
 4      0 => int 0
 5      1 => int 1
 6      2 => int 2
 7      3 => int 3
 8      4 => int 4
 9      5 => int 5
10      6 => int 6
11      7 => int 7
12      8 => int 8
13      9 => int 9

It should be noted that the collapse method does not recursively collapse inner arrays. The following code sample will create another collection, this time with a nested array:

 1use Illuminate\Support\Collection;
 2 
 3$first = [
 4    0, 1, 2, 3, 4
 5];
 6 
 7$second = [
 8    [5, 6, 7, 8 , 9]
 9];
10 
11$collection = new Collection([$first, $second]);

If we collapsed the $collection, the result would be similar to the following output:

 1object(Illuminate\Support\Collection)
 2  protected 'items' =>
 3    array
 4      0 => int 0
 5      1 => int 1
 6      2 => int 2
 7      3 => int 3
 8      4 => int 4
 9      5 =>
10        array
11          0 => int 5
12          1 => int 6
13          2 => int 7
14          3 => int 8
15          4 => int 9

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