[8.x] Add reduce with keys to collections and lazy collections (#35839)

* add reduce with keys to collections * add reduce with keys to lazy collections * add test for reduce with keys * fix style

Author: mokhosh

src/Illuminate/Collections/Collection.php

@@ -884,6 +884,24 @@ public function reduce(callable $callback, $initial = null)
  return array_reduce($this->items, $callback, $initial);
  }
 
+ /**
+ * Reduce an associative collection to a single value.
+ *
+ * @param callable $callback
+ * @param mixed $initial
+ * @return mixed
+ */
+ public function reduceWithKeys(callable $callback, $initial = null)
+ {
+ $result = $initial;
+
+ foreach ($this->items as $key => $value) {
+ $result = $callback($result, $value, $key);
+ }
+
+ return $result;
+ }
+
  /**
  * Replace the collection items with the given items.
  *

src/Illuminate/Collections/LazyCollection.php

@@ -845,6 +845,24 @@ public function reduce(callable $callback, $initial = null)
  return $result;
  }
 
+ /**
+ * Reduce an associative collection to a single value.
+ *
+ * @param callable $callback
+ * @param mixed $initial
+ * @return mixed
+ */
+ public function reduceWithKeys(callable $callback, $initial = null)
+ {
+ $result = $initial;
+
+ foreach ($this as $key => $value) {
+ $result = $callback($result, $value, $key);
+ }
+
+ return $result;
+ }
+
  /**
  * Replace the collection items with the given items.
  *

tests/Support/SupportCollectionTest.php

@@ -3592,6 +3592,20 @@ public function testReduce($collection)
  }));
  }
 
+ /**
+ * @dataProvider collectionClassProvider
+ */
+ public function testReduceWithKeys($collection)
+ {
+ $data = new $collection([
+ 'foo' => 'bar',
+ 'baz' => 'qux',
+ ]);
+ $this->assertEquals('foobarbazqux', $data->reduceWithKeys(function ($carry, $element, $key) {
+ return $carry .= $key.$element;
+ }));
+ }
+
  /**
  * @dataProvider collectionClassProvider
  */