[5.3] Add split method to collection class (#15302)

* add split function to collection

* fix nitpicks

* fix cs

* more cs fixes

* moar cs

* return new instance

src/Illuminate/Support/Collection.php

@@ -920,6 +920,23 @@ public function slice($offset, $length = null)
         return new static(array_slice($this->items, $offset, $length, true));
     }
 
+    /**
+     * Split a collection into a certain number of groups.
+     *
+     * @param  int  $numberOfGroups
+     * @return static
+     */
+    public function split($numberOfGroups)
+    {
+        if ($this->isEmpty()) {
+            return new static;
+        }
+
+        $groupSize = ceil($this->count() / $numberOfGroups);
+
+        return $this->chunk($groupSize);
+    }
+
     /**
      * Chunk the underlying collection array.
      *

tests/Support/SupportCollectionTest.php

@@ -1554,6 +1554,54 @@ public function testCollectonFromTraversableWithKeys()
         $collection = new Collection(new \ArrayObject(['foo' => 1, 'bar' => 2, 'baz' => 3]));
         $this->assertEquals(['foo' => 1, 'bar' => 2, 'baz' => 3], $collection->toArray());
     }
+
+    public function testSplitCollectionWithADivisableCount()
+    {
+        $collection = new Collection(['a', 'b', 'c', 'd']);
+
+        $this->assertEquals(
+            [['a', 'b'], ['c', 'd']],
+            $collection->split(2)->map(function (Collection $chunk) {
+                return $chunk->values()->toArray();
+            })->toArray()
+        );
+    }
+
+    public function testSplitCollectionWithAnUndivisableCount()
+    {
+        $collection = new Collection(['a', 'b', 'c']);
+
+        $this->assertEquals(
+            [['a', 'b'], ['c']],
+            $collection->split(2)->map(function (Collection $chunk) {
+                return $chunk->values()->toArray();
+            })->toArray()
+        );
+    }
+
+    public function testSplitCollectionWithCountLessThenDivisor()
+    {
+        $collection = new Collection(['a']);
+
+        $this->assertEquals(
+            [['a']],
+            $collection->split(2)->map(function (Collection $chunk) {
+                return $chunk->values()->toArray();
+            })->toArray()
+        );
+    }
+
+    public function testSplitEmptyCollection()
+    {
+        $collection = new Collection();
+
+        $this->assertEquals(
+            [],
+            $collection->split(2)->map(function (Collection $chunk) {
+                return $chunk->values()->toArray();
+            })->toArray()
+        );
+    }
 }
 
 class TestAccessorEloquentTestStub