spaces or %20 in links turn into + signs when page is sent as an email

Question

I am creating a web app that accepts input of news items (title, article, url). It has a page news.php which creates a summary of all news items inputted for specified dates, like so:

News
4/25/2010

Title 1
[URL 1]
Article 1

Title 2
[URL 2]
Article 2

and so on...

I have two other pages, namely preview.php and send.php , both of which call news.php through a file_get_contents() call.

Everything works fine except when the URL contains spaces. During Preview, the urls get opened (FF: spaces are spaces, Chrome: spaces are %20). However, during Send, when received as emails, the urls don't get opened, because the spaces are converted into + signs.

For example:

1. Preview in FF: http://www.example.com/this is the link.html
2. Preview in Chrome: http://www.example.com/this%20is%20the%20link.html
3. Viewed as email in both browsers: http://www.example.com/this+is+the+link.html

Only #3 doesn't work (link doesn't get opened).

Why are the spaces in the urls correct (spaces or %20) when previewed, but incorrect (+) when received in the emails, when in fact, the same page is generated by the same news.php?

Any help appreciated :)

---

EDIT:

preview.php:

$HTML_version = file_get_contents('news.php');
echo $HTML_version;

send.php

$HTML_version = file_get_contents('news.php');
$body = "$notice_text

--$mime_boundary
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit

$TEXT_version

--$mime_boundary
Content-Type: text/html; charset=us-ascii
Content-Transfer-Encoding: 7bit

$HTML_version

--$mime_boundary--";
//some other code here to send the email

news.php:

<a href="<?php echo $url ?>">attachment</a>
//the $url there contains spaces

Answer 1

The + signs are a legacy substitute for space or %20, so they should work fine. Since they don't I would recommend that you manually converted all spaces in the URL to %20. That should fix the problem.

Answer 2

What mail client are you using? Mail clients' handling of HTML is subject to extreme limitations and bugs.

<a href="<?php echo $url ?>">attachment</a>
//the $url there contains spaces

URLs don't contain spaces, by definition. If you include a space in a link in HTML:

<a href="x y.z">

the browser will typically fix your error, by encoding to x%20y.z. However this is not a standardised behaviour and you should not rely on it. It is, I suppose, possible that some dodgy mail client could be misguidedly ‘fixing’ it up to x+y.z instead, which wouldn't work because + in the path part of a URL does not mean a space.

Use rawurlencode() for URL-encoding. With this function, spaces are converted to %20, which is appropriate for URL path-parts and query strings. PHP's misleadingly-named urlencode() function encodes to + instead, which is only appropriate in form data in the query string.

You also need to use htmlspecialchars() any time you output a string to HTML.

$name= 'this is the link';
$url= 'http://www.example.com/'.rawurlencode($name).'.html';

<a href="<?php echo htmlspecialchars($url); ?>">link</a>