How to change the http in frontend, CheckOut Page to https in front end for magento

Add this code in relevant html pages for Check Out page in Magento

<?php
        $loadFromSSL = $_SERVER['SERVER_PORT']==443?true:false;
        if($loadFromSSL)
        {echo str_replace("http://","https://",
$this->getChildHtml('head_phone_block'));
        }else { echo $this->getChildHtml('head_phone_block'); }?>       
            <?php //echo $this->getChildHtml('head_phone_block')?>