feature: support head() and last()

stubs/helpers.stubphp

@@ -81,6 +81,32 @@ class NullObject {
     }
 }
 
+/**
+ * Get the first element of an array. Useful for method chaining.
+ *
+ * @template TValue
+ * @template TParam of TValue[]
+ * @param  TParam  $array
+ * @return (TParam is non-empty-array ? TValue : false)
+ */
+function head($array)
+{
+    return reset($array);
+}
+
+/**
+ * Get the last element from an array.
+ *
+ * @template TValue
+ * @template TParam of TValue[]
+ * @param  TParam  $array
+ * @return (TParam is non-empty-array ? TValue : false)
+ */
+function last($array)
+{
+
+}
+
 /**
  * Provide access to optional objects.
  *