[TYPO3-workspace] Get preview link

[alkativo]

Hi,

i made a backend extension that export the content from a page as aray in php file. How can i do this with a preview link. I only can use the external pre link  I need the ADMCMD_prev cookie. But i am in backend not in frontend. I found this

function ADMCMD_preview(){
        $inputCode = t3lib_div::_GP('ADMCMD_prev');
        // If no inputcode and a cookie is set, load input code from cookie:
        if (!$inputCode && $_COOKIE['ADMCMD_prev'])    {
            $setFromCookie = TRUE;
            $inputCode = $_COOKIE['ADMCMD_prev'];
        }
        // If inputcode now, look up the settings:
        if ($inputCode)    {