Problem with mixing Javascript the PHP

Question

I am trying to assign values in javascript assigned from PHP and the use document.write() to output them. The problem is when I do this, a complete blank screen shows up but no errors are ever thrown. But if I take the PHP out and put in a value such as 'ABC' it works. And example of my code can be this:

var comment_text="<?php echo $value['comment_text'];?>";
var bodyelement = document.getElementsByTagName('body')[0];
        var newdiv = document.createElement('div');
newdiv.style.textAlign = 'center';
            newdiv.style.zIndex = 10001;
            newdiv.style.left = (<?php echo $comment_x;?>+getPos('browserwindow',"Left")-23) + 'px';
            newdiv.style.top = (<?php echo $comment_y;?>+getPos('browserwindow',"Top")-90) + 'px';
            newdiv.style.position = 'absolute';
newdiv.innerHTML = comment_text;
        bodyelement.appendChild(newdiv);

I do have an PHP error log and no errors are beign thrown either. The values are retrieved from the database, the probem comes with outputting them. *UPDATE* Ok, I had this problem before.

Basically a newline is created like this:

var comment_text="cool Beans

";

I have tried to remove the newline with string replace but doesn't seem to work. Why would a new line like this cause this error?

Check your Apache logs for errors. If you're getting a blank screen it's possible that PHP errors are showing up in the log. — Fareesh Vijayarangam
– Fareesh Vijayarangam, Commented Mar 22, 2011 at 13:05
what is output -> is it $commnent_x, $comment_y, and $value['comment_text'] show up ? — bensiu
– bensiu, Commented Mar 22, 2011 at 13:06
+1 for php in html in a string in php to be passed to javascript — Matt
– Matt, Commented Mar 22, 2011 at 13:08
$commnent_x, $comment_y, etc has no affect. Only when I echo $value['comment_text'] does the blank screen occur — Devin Dixon
– Devin Dixon, Commented Mar 22, 2011 at 13:13

Jakub · Accepted Answer · 2011-03-22 13:12:30Z

3

Your issue is cleary in the output from PHP. If you get a blank page, means you most likely have a PHP issue that is HALTING the processing of said page.

As PHP is parsed before anything is sent to the viewer, this will result in a blank / error page.

When you substitute your $value['comment_text'] for ABC you remove the location that causes the error.

I am going to assume that $value['comment_text'] is either a result of a function, or a Database query, try just outputting the $value['comment_text'] first, then worry about sticking it in JS (which will work if your PHP code works).

As I don't see any of your PHP code, I cannot help you further.

answered Mar 22, 2011 at 13:12

Jakub

20.5k8 gold badges67 silver badges93 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

Devin Dixon Over a year ago

The values are retrieved from the database yes. The values are retrieved because I've done a print_r($value) and everything output. So the information is there.

Jakub Over a year ago

are your database results in array() form or object?

Czechnology Over a year ago

@Devin Dixon, you should escape the quotes in comment_text: <?php echo addslashes($value['comment_text']); ?>.

Arc Over a year ago

@Devin Dixon and Czechnology, I would recommend using json_encode() rather than addslashes(): var comment_text="<?php echo $value['comment_text'];?>" should be written as var comment_text=<?php echo json_encode($value['comment_text']);?>, which also does the quoting for you and supports special characters etc.

Arc · Accepted Answer · 2011-03-22 14:02:42Z

1

Use

var comment_text=String(<?php echo json_encode($value['comment_text']);?>);

instead of

var comment_text="<?php echo $value['comment_text'];?>";

This will protect you from cross-site-scripting attacks by escaping all special characters like backslashes, quotes or line feeds.

The String(...) ensures that comment_text has type String and is not interpreted as a number (if $value['comment_text'] is has a number type).

answered Mar 22, 2011 at 14:02

Arc

11.4k4 gold badges56 silver badges76 bronze badges

Comments

Andrew · Accepted Answer · 2011-03-22 13:16:45Z

0

If PHP is causing an error (sounds like it is) you can turn on your error reporting to see the issues

error_reporting(E_ALL)

answered Mar 22, 2011 at 13:16

Andrew

10k10 gold badges66 silver badges104 bronze badges

Comments

Devin Dixon · Accepted Answer · 2011-03-22 13:24:28Z

0

The solution was just using trim.

echo trim($value['comment_text']);

answered Mar 22, 2011 at 13:24

Devin Dixon

12.5k24 gold badges101 silver badges181 bronze badges

2 Comments

Jakub Over a year ago

How is this a solution? What actually broke it? Spaces in your comment? OR your newline method?

Devin Dixon Over a year ago

Its a solution that apparentls worked sometimes but not others. json_encode works %100 of the time

Joseph Le Brech · Accepted Answer · 2011-03-22 13:28:36Z

0

I recommend you use a heredoc for the javascript code with %s in the js. and use sprintf to substitute the variables.

answered Mar 22, 2011 at 13:28

Joseph Le Brech

6,64911 gold badges54 silver badges84 bronze badges

Collectives™ on Stack Overflow

Problem with mixing Javascript the PHP

5 Answers 5

4 Comments

Comments

Comments

2 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

4 Comments

Comments

Comments

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related