Le portail francophone de la géomatique

Quelqu'un peut m'expliquer l'erreur suivante:

Fatal error: Uncaught exception 'CartocommonException' with message 'Error [2, Cannot modify header information - headers already sent by (output started at /exec/applis/sglvit/G01R02C01/cartoweb3/projects/vitale/plugins/addPoint/client/ClientAddPoint.php:59), /exec/applis/sglvit/G01R02C01/cartoweb3/client/FormRenderer.php, 452] Backtrace: file: 290 - /exec/applis/sglvit/G01R02C01/cartoweb3/common/Common.php call: Common::cartowebErrorHandler() file: 452 - /exec/applis/sglvit/G01R02C01/cartoweb3/client/FormRenderer.php call: Common::cartowebErrorHandler(2, "Cannot modify header information - headers already sent by (outp...", "/exec/applis/sglvit/G01R02C01/cartoweb3/client/FormRenderer.php", 452, Array(1)) file: 452 - /exec/applis/sglvit/G01R02C01/cartoweb3/client/FormRenderer.php call: header("HTTP/1.1 500 Internal Server Error") file: 1226 - /exec/applis/sglvit/G01R02C01/cartoweb3/client/Cartoclient.php call: FormRenderer->showFailure(Object(SoapFaultWrapper)) file: 39 - /exec/applis/sglvit/G01R02C01/cartoweb3/htdo in /exec/applis/sglvit/G01R02C01/cartoweb3/common/Common.php on line 290

je ne comprends pas le fait que les headers sont déja définis dans monPlugin le code du plugin est le suivant:

<?php

require_once('smarty/Smarty.class.php');

class AddPointState {
   
    public $action;// steps pour ajoutsite
    public $formMessage;// message eventuel en tete de form (erreur)
    public $point_orig; // point lors du 1er click (add ou move)
    public $message;// Msg eventuel retour du server (erreur, info...)
    public $lastAddMoveTime;// Add for avoiding wrong cache result after add operation
}


class ClientAddPoint extends ClientPlugin implements ToolProvider
{

const TOOL_ADD_POINT = 'addPoint';

private $log;
protected $addPointState;

public function __construct()
{parent::__construct();
$this->log =& LoggerManager::getLogger(__CLASS__);
        $this->log->debug('FPTRACE AddPoint construct');
}

public function handleMainmapTool(ToolDescription $tool, Shape $mainmapShape) {
                 return $mainmapShape;   
    }
     /**
     * @see ToolProvider::handleKeymapTool()
     */
    public function handleKeymapTool(ToolDescription $tool,
                            Shape $keymapShape) {
        /* nothing to do */
    }
    /**
     * @see ToolProvider::handleApplicationTool()
     */
    public function handleApplicationTool(ToolDescription $tool) {}
/** Surcharge parent function
     * @see ToolProvider::getTools()
     */
    public function getTools() {
        return array( new ToolDescription(self::TOOL_ADD_POINT, true, 50));
    }

}
?>