Implement Countable interface in OptionsPropertyGroup

This is really needed in OptionsPropertyRootGroup, but makes sense here
as well.

Signed-off-by: Michal Čihař <michal@cihar.com>

libraries/properties/options/OptionsPropertyGroup.php

@@ -14,7 +14,7 @@
  * @todo    modify descriptions if needed, when the options are integrated
  * @package PhpMyAdmin
  */
-abstract class OptionsPropertyGroup extends OptionsPropertyItem
+abstract class OptionsPropertyGroup extends OptionsPropertyItem implements \Countable
 {
     /**
      * Holds a group of properties (PMA\libraries\properties\options\OptionsPropertyItem instances)
@@ -87,6 +87,18 @@ public function getProperties()
      */
     public function getNrOfProperties()
     {
+        if (is_null($this->_properties)) {
+            return 0;
+        }
         return count($this->_properties);
     }
+
+    /**
+     * Countable interface implementation.
+     *
+     * @return int
+     */
+    public function count() {
+        return $this->getNrOfProperties();
+    }
 }

test/classes/properties/options/groups/OptionsPropertyRootGroupTest.php

@@ -50,4 +50,17 @@ public function testGetItemType()
         );
     }
 
+    /**
+     * Test for contable interface
+     *
+     * @return void
+     */
+    public function testCountable()
+    {
+        $this->assertEquals(
+            0,
+            count($this->object)
+        );
+    }
+
 }