Fix types

src/HAB/Solr/Command/CommandInterface.php

@@ -23,6 +23,8 @@
 
 namespace HAB\Solr\Command;
 
+use HAB\Solr\ParamBag;
+
 /**
  * Interface of a Solr command.
  *
@@ -42,7 +44,7 @@ interface CommandInterface
     /**
      * Return parameters.
      *
-     * @return array
+     * @return ParamBag
      */
     public function getParameters ();
 
@@ -61,4 +63,4 @@ interface CommandInterface
      */
     public function getResult ();
         
-}
+}
\ No newline at end of file

src/HAB/Solr/Command/Invoker.php

@@ -103,7 +103,7 @@ class Invoker
      */
     public function getParameters ()
     {
-        if (is_null($this->parameters)) {
+        if ($this->parameters === null) {
             $this->setParameters(new ParamBag());
         }
         return $this->parameters;
@@ -113,7 +113,7 @@ class Invoker
      * Set parameters.
      *
      * @param  ParamBag $parameters
-     * @return
+     * @return void
      */
     public function setParameters (ParamBag $parameters)
     {
@@ -131,4 +131,4 @@ class Invoker
     {
         return sprintf('%s=%s', urlencode($name), urlencode($value));
     }
-}
+}
\ No newline at end of file