better documentation for Command in db Connection

framework/db/Connection.php

@@ -180,6 +180,7 @@ class Connection extends Component
      * This property is mainly managed by [[open()]] and [[close()]] methods.
      * When a DB connection is active, this property will represent a PDO instance;
      * otherwise, it will be null.
+     * @see pdoClass
      */
     public $pdo;
     /**
@@ -280,10 +281,18 @@ class Connection extends Component
         'cubrid' => 'yii\db\cubrid\Schema', // CUBRID
     ];
     /**
-     * @var string Custom PDO wrapper class. If not set, it will use "PDO" or "yii\db\mssql\PDO" when MSSQL is used.
+     * @var string Custom PDO wrapper class. If not set, it will use [[PDO]] or [[yii\db\mssql\PDO]] when MSSQL is used.
+     * @see pdo
      */
     public $pdoClass;
     /**
+     * @var string the class used to create new database [[Command]] objects. If you want to extend the [[Command]] class,
+     * you may configure this property to use your extended version of the class.
+     * @see createCommand
+     * @since 2.0.7
+     */
+    public $commandClass = 'yii\db\Command';
+    /**
      * @var boolean whether to enable [savepoint](http://en.wikipedia.org/wiki/Savepoint).
      * Note that if the underlying DBMS does not support savepoint, setting this property to be true will have no effect.
      */
@@ -338,11 +347,6 @@ class Connection extends Component
      */
     public $masters = [];
     /**
-     * @var string the class name of the [[Command]] object.
-     * @since 2.0.7
-     */
-    public $commandClass = 'yii\db\Command';
-    /**
      * @var array the configuration that should be merged with every master configuration listed in [[masters]].
      * For example,
      *