Add helper function for checking if an object is an array-like object.

Added support for traversable objects in `BaseHtml` and `ArrayHelper`

framework/helpers/BaseArrayHelper.php

@@ -680,7 +680,7 @@ class BaseArrayHelper
      * Check whether an array or [[\Traversable]] contains an element.
      *
      * This method does the same as the PHP function [in_array()](http://php.net/manual/en/function.in-array.php)
-     * but it does not only work for arrays but also objects that implement the [[\Traversable]] interface.
+     * but additionally works for objects that implement the [[\Traversable]] interface.
      * @param mixed $needle The value to look for.
      * @param array|\Traversable $haystack The set of values to search.
      * @param boolean $strict Whether to enable strict (`===`) comparison.
@@ -706,6 +706,21 @@ class BaseArrayHelper
         return false;
     }
 
+    /**
+     * Checks whether a variable is an array or [[\Traversable]].
+     *
+     * This method does the same as the PHP function [is_array()](http://php.net/manual/en/function.is-array.php)
+     * but additionally works objects that implement the [[\Traversable]] interface.
+     * @param mixed $var The variable being evaluated.
+     * @return boolean whether $var is array-like
+     * @see http://php.net/manual/en/function.is_array.php
+     * @since 2.0.8
+     */
+    public static function isTraversable($var)
+    {
+        return is_array($var) || $var instanceof \Traversable;
+    }
+
     /**
      * Checks whether an array or [[\Traversable]] is a subset of another array or [[\Traversable]].
      *