通过JavaScript检查php会话，如果它不存在不应该导致任何错误

var secret_photo
var secret_name

if (!<?php echo isset($_SESSION['fb_item'])?'true':'false'; ?>) {
if($.cookie("domain[user]")){
secret_photo = 'noavatar.png';
secret_name = 'admin';
}
} else {
secret_photo = <?php echo json_encode($_SESSION['fb_item']['url']); ?>;
secret_name = <?php echo json_encode($_SESSION['fb_item']['name']); ?>;
}

I need to set php session to html using JavaScript .There is 2 logins , one is the facebook and the other is my own login system, facebook uses session and my own login sets cookie.

When I login by facebook , things are good , but if I login using my own login system , that echo check is going to cause problem , so how am I going to fix it ? Check if the session is available or not even if it doesn't exist it wont cause any problem.

You are probably encounter an error at the bottom of your code. You can't access $_SESSION['fb_item'] if it doesn't exist, it either shows a Notice or generate wrong js code secret_photo = ;. Just move condition to php side:

var secret_photo
var secret_name

<?php if(!isset($_SESSION['fb_item'])):?>
    if($.cookie("domain[user]")){
        secret_photo = 'noavatar.png';
        secret_name = 'admin';
    }
<?php else:?>
    secret_photo = <?php echo json_encode($_SESSION['fb_item']['url']); ?>;
    secret_name = <?php echo json_encode($_SESSION['fb_item']['name']); ?>;
<?php endif;?>

<script type="text/javascript">
var secret_photo
var secret_name
<?php if(!isset($_SESSION['fb_item'])){?>
    if($.cookie('user')){
        secret_photo = 'noavatar.png';
        secret_name = 'admin';
    }
<?php }else{?>
    secret_photo = <?php echo json_encode($_SESSION['fb_item']['url']); ?>;
    secret_name = <?php echo json_encode($_SESSION['fb_item']['name']); ?>;
<?php }?>
</script>