AJAX，返回php字符串并传递给javascript函数

I have a db that stores some email content. I make an ajax request for the email content, when that's returned I want to pass the content to a function that will display a popup with the email content in there. The problem I have is that there are html tags in the email content, which I would like to keep if possible.

I have tried using json_encode and rawurlencode/decodeURIComponent but either the encoded string breaks my below javascript and just displays the email in the page or I get a javascript "Unterminated string literal" error thrown.

var message = "<a href=\"javascript:viewMessage('"+aData[8]+"');\" class=\"glyphicons glyphicons-circle-info\" id=\"comms_msg\"></a>";

Can anyone point me in the right direction?

If jquery is option, look at this example

$(function () {
    var viewMessage=function(msg){
        $('#popup').html(msg); // <div id="popup"></div>
    }
    $.ajax({
        type: 'post',
        url: "/request/email/content/", // request for email content
        dataType: "html",
        success: function (data) {
            viewMessage(data);
        }
    });
});

</div>