Add AbstractCollection::flatten() method

formwork/src/Data/AbstractCollection.php

@@ -386,6 +386,16 @@ abstract class AbstractCollection implements Arrayable, Countable, Iterator
         return Arr::pluck($this->data, $key, $default);
     }
 
+    /**
+     * Flatten the collection items up to the specified depth
+     */
+    public function flatten(int $depth = PHP_INT_MAX): static
+    {
+        $collection = $this->clone();
+        $collection->data = Arr::flatten($collection->data, $depth);
+        return $collection;
+    }
+
     /**
      * Filter the collection using the key from each item
      */

formwork/src/Utils/Arr.php

@@ -436,6 +436,49 @@ class Arr
         return $result;
     }
 
+    /**
+     * Flatten array items up to the specified depth
+     *
+     * @param array<mixed> $array
+     *
+     * @return array<mixed>
+     */
+    public static function flatten(array $array, int $depth = PHP_INT_MAX): array
+    {
+        if ($depth === 0) {
+            return $array;
+        }
+
+        if ($depth < 0) {
+            throw new UnexpectedValueException(sprintf('%s() expects a non-negative depth', __METHOD__));
+        }
+
+        $result = [];
+
+        foreach ($array as $value) {
+            if ($value instanceof Arrayable) {
+                $value = $value->toArray();
+            }
+            if ($value instanceof Traversable) {
+                $value = iterator_to_array($value);
+            }
+
+            if (!is_array($value)) {
+                $result[] = $value;
+                continue;
+            }
+
+            if ($depth > 1) {
+                $value = static::flatten($value, $depth - 1);
+            }
+            foreach ($value as $val) {
+                $result[] = $val;
+            }
+        }
+
+        return $result;
+    }
+
     /**
      * Sort an array with the given options
      *