<script type="text/javascript">
    //IE5+, Mozilla 1.0+, Opera 7+
    function getClientWidth()
    {
        return document.compatMode=='CSS1Compat' && !window.opera?document.documentElement.clientWidth:document.body.clientWidth;
    }
    function getClientHeight()
    {
        return document.compatMode=='CSS1Compat' && !window.opera?document.documentElement.clientHeight:document.body.clientHeight;
    }
</script>

<?php
$screenWidth='<script type="text/javascript">document.write("screen.width="+ getClientWidth());</script>';
$screenHeight='<script type="text/javascript">document.write("screen.height="+ getClientHeight());</script>';
echo $screenWidth;
echo $screenHeight;
?>