Passage de variable dans popup

echo'</h2>

<div class="imgeetab">

<a href="../'.$nom_dir2.'" title="'.$rezresidences['etab_nom'].'"><img src="../images_etab/'.$rezresidences['etab_image'].'" border="0" alt="'.$rezresidences['etab_nom'].'" align="absmiddle"/></a>

</div>

<div class="textegeneral"><br />



<p class="accrocheetab">'.$rezresidences['etab_accrocheFr'].'</p><br />



<div class="lien_etab_info">

<a href="../'.$nom_dir2.'" title="'.$rezresidences['etab_nom'].'"> plus d\'infos</a>

</div>

<div class="lien_etab_info">

<form name="frmres" id="frmres" method="post" action="" >

<input type="hidden" name="id_etab" id="id_etab" value="'.$rezresidences['etab_id'].'"/>

<input type="image" src="../images/reserver.jpg"  onclick="fenetreresa(frmres)" name="button" id="button" class="boutonreserver" alt="Réserver"/>

</form>

</div>

</div>

<br clear="all"/>

</div>';

<script type="text/javascript">

function fenetreresa(var1){



var hauteur_popup=180;



  var H = (screen.height - hauteur_popup) / 2;



  var largeur_popup=400;



  var L = (screen.width - largeur_popup) / 2;



window.open('reservations.php',var1,'resizable=no, locationbar=no,menubar=no,personalbar=no,toolbar=no, scrollbars=yes, status=yes,width=900,height=1000,Left='+L+',Top='+H+'');



} 

</script>

<input type="image" src="../images/reserver.jpg"  onclick="fenetreresa(frmres)" name="button" id="button" class="boutonreserver" alt="Réserver"/>

window.open("reservations.php?var1="+var1

<script type="text/javascript">

function fenetreresa(var1){



var hauteur_popup=180;



  var H = (screen.height - hauteur_popup) / 2;



  var largeur_popup=400;



  var L = (screen.width - largeur_popup) / 2;



window.open("reservations.php?var1="+var1, 'resizable=no, locationbar=no,menubar=no,personalbar=no,toolbar=no, scrollbars=yes, status=yes,width=900,height=1000,Left='+L+',Top='+H+'');



} 

</script>

<input type="image" src="../images/reserver.jpg"  onclick="fenetreresa('.$rezresidences['etab_id'].')" name="button" id="button" class="boutonreserver" alt="Réserver"/>

 $_SESSION['resa']['etab']=$rezresidences['etab_id'];



 $_SESSION['resa']['etab']=$_POST['id_etab'];



 $_SESSION['resa']['etab']=var1;



 $_SESSION['resa']['etab']=$var1;