Add get all sessions method

Author: alekciy

lib/remote/HttpCommandExecutor.php

@@ -23,6 +23,7 @@ class HttpCommandExecutor implements WebDriverCommandExecutor {
    *   http://code.google.com/p/selenium/wiki/JsonWireProtocol#Command_Reference
    */
   protected static $commands = array(
+    DriverCommand::GET_ALL_SESSIONS =>        array('method' => 'GET', 'url' => '/sessions'),
     DriverCommand::ACCEPT_ALERT =>            array('method' => 'POST', 'url' => '/session/:sessionId/accept_alert'),
     DriverCommand::ADD_COOKIE =>              array('method' => 'POST', 'url' => '/session/:sessionId/cookie'),
     DriverCommand::CLEAR_ELEMENT =>           array('method' => 'POST', 'url' => '/session/:sessionId/element/:id/clear'),

lib/remote/RemoteWebDriver.php

@@ -461,6 +461,29 @@ public function getSessionID() {
     return $this->sessionID;
   }
 
+  /**
+   * Get all selenium sessions.
+   *
+   * @param string $url The url of the remote server
+   * @param int $timeout_in_ms
+   * @return array
+   */
+  public static function getAllSessions(
+    $url = 'http://localhost:4444/wd/hub',
+    $timeout_in_ms = 300000
+  ) {
+    $executor = new HttpCommandExecutor($url);
+    $executor->setConnectionTimeout($timeout_in_ms);
+
+    $command = new WebDriverCommand(
+      null,
+      DriverCommand::GET_ALL_SESSIONS,
+      array()
+    );
+
+    return $executor->execute($command)->getValue();
+  }
+
   public function execute($command_name, $params = array()) {
     $command = new WebDriverCommand(
       $this->sessionID,