Question

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Pass a PHP string to a Javascript variable (and escape newlines)

So, essentially I am trying to pass a string from a PHP page as an argument for a javascript function. The PHP is included in the page that the script is on, but they are in two separate files.

However, whenever I try to pass a string, it stops the javascript from running. I can pass PHP integers, but not strings. Is it possible to fix this? I’ve been looking around the internet for what might be causing my error, but I can’t find anything. Any help would be greatly appreciated.

This is the PHP and HTML. The function runs when submit is clicked.

$comment = "7b";
echo"
    <table>
         <p><input type='text' id='newPostComment' value='' placeholder='WRITE YOUR COMMENT HERE...' size='35'/><input type='submit' value='UPLOAD' onclick='uploadPostComment($parentID, $comment);fetchComment()'/></p>
    </table>

This is the javascript function.

function uploadPostComment(PostCID, Comment){

      var PostCommentData = "fsPostID="+PostCID;
      PostCommentData += "&fsPostComment="+Comment;

      var xmlHttp = new XMLHttpRequest();
      xmlHttp.open("post", "uploadPostComment.php", true);

      xmlHttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
      xmlHttp.setRequestHeader("Content-length", PostCommentData.length);
      xmlHttp.setRequestHeader("Connection", "close");

      xmlHttp.onreadystatechange = function()
         {
             if(xmlHttp.readyState == 4)
             {
                if(xmlHttp.status == 200)
                {
                    alert("Message Posted");
                }
                else
                {
                    alert("Oh no, an error occured2"); 
                }
             }
         };
         xmlHttp.send(PostCommentData);}

Answer 1

echo"
    <table>
         <p><input type='text' id='newPostComment' value='' placeholder='WRITE YOUR COMMENT HERE...' size='35'/><input type='submit' value='UPLOAD' onclick='uploadPostComment(\"$parentID\", \"" . str_replace('"', '\"', $comment) . "\");fetchComment()'/></p>
    </table>

You need to quote the fields. If your field is an integer it does not need to be quoted, if it is a string it needs to be. I quoted both because I don’t know if parentID is a string id or a numeric id. Do what your application needs of course.

Update: in regards to Michael’s comment about breaking if comment contains a quote. We now escape all double quotes in $comment to prevent that.