[9.x] Adds collection key first/last. (#41450)

* Adds key first/last.

* Update Collection.php

* Update Collection.php

Co-authored-by: Taylor Otwell <[email protected]>

Author: DarkGhostHunter

src/Illuminate/Collections/Collection.php

@@ -389,6 +389,16 @@ public function first(callable $callback = null, $default = null)
         return Arr::first($this->items, $callback, $default);
     }
 
+    /**
+     * Get the first key of the collection.
+     *
+     * @return mixed
+     */
+    public function firstKey()
+    {
+        return array_key_first($this->items);
+    }
+
     /**
      * Get a flattened array of the items in the collection.
      *
@@ -694,6 +704,16 @@ public function last(callable $callback = null, $default = null)
         return Arr::last($this->items, $callback, $default);
     }
 
+    /**
+     * Get the last key of the collection.
+     *
+     * @return mixed
+     */
+    public function lastKey()
+    {
+        return array_key_last($this->items);
+    }
+
     /**
      * Get the values of a given key.
      *

tests/Support/SupportCollectionTest.php

@@ -69,6 +69,17 @@ public function testFirstWithDefaultAndWithoutCallback($collection)
         $this->assertSame('default', $result);
     }
 
+    public function testFirstKey()
+    {
+        $data = new Collection(['foo' => 'bar', 'baz' => 'quz', 'qux' => 'quux']);
+
+        $this->assertSame('foo', $data->firstKey());
+
+        $data = new Collection(['foo', 'bar', 'baz', 'quz']);
+
+        $this->assertSame(0, $data->firstKey());
+    }
+
     /**
      * @dataProvider collectionClassProvider
      */
@@ -330,6 +341,17 @@ public function testLastWithDefaultAndWithoutCallback($collection)
         $this->assertSame('default', $result);
     }
 
+    public function testLastKey()
+    {
+        $data = new Collection(['foo' => 'bar', 'baz' => 'quz', 'qux' => 'quux']);
+
+        $this->assertSame('qux', $data->lastKey());
+
+        $data = new Collection(['foo', 'bar', 'baz', 'quz']);
+
+        $this->assertSame(3, $data->lastKey());
+    }
+
     public function testPopReturnsAndRemovesLastItemInCollection()
     {
         $c = new Collection(['foo', 'bar']);