Maybe you guys know that I've been working on a service called MyWapBlog.com which lets peoples create/manage Mobile blogs using their mobile phones. In the course of the development I've learnt great deal about mobile websites and their dynamic generation, and I'm sharing a bit of it here in this post.
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How do you generate dynamic (X)HTML Pages using PHP? Simple:
<html xmlns="http://www.w3.org/1999/xhtml" dir="ltr">
<head>
<title>Sometitle</title>
</head>
<body>
<h1>Hello</h1>
<p><?php echo date('h:i A, j-M-y'); ?></p>
</body>
</html>
And if you look at XHTML MP pages, their source look like the following:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//WAPFORUM//DTD XHTML Mobile 1.0//EN" "http://www.wapforum.org/DTD/xhtml-mobile10.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
...
...
So you see these pages have a different document type and some other differences. So will the following code work and generate a valid WAP 2.0 page?:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//WAPFORUM//DTD XHTML Mobile 1.0//EN" "http://www.wapforum.org/DTD/xhtml-mobile10.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Sometitle</title>
</head>
<body>
<h1>Hello</h1>
<p><?php echo date('h:i A, j-M-y'); ?></p>
</body>
</html>
The answer is “NO”? Why? Because XHTML MP pages needs to be served with a different Content-Type than what is generated by .PHP files. Normally when you runa s PHP Script and it outputs something, the content is served with Content-Type: text/html
What is Content-Type?
It is a Header (information about a particular resource) returned to Browser when it requests something from a server. When you request an image, the server return the image with the header image/png, image/jpeg etc. letting the browser know how the returned content is to be interpreted.
PHP scripts can return contents of any type (using
the header() function), from text to
images and PDFs to ZIPs. And therfore
if we want to generate XHTML MP pages, it can even do that
without doubt.
So what we need to do is, just change the above code a bit adding a new line at the top so that the whole code look like the following:
<?php header("Content-type: application/vnd.wap.xhtml+xml; charset=UTF-8");?>
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//WAPFORUM//DTD XHTML Mobile 1.0//EN" "http://www.wapforum.org/DTD/xhtml-mobile10.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Sometitle</title>
</head>
<body>
<h1>Hello</h1>
<p><?php echo date('h:i A, j-M-y'); ?></p>
</body>
</html>
This will tell the browser that the content we are going to serve is of the type XHTML MP. We always use the charset UTF-8 for these pages, which is also told to the requesting browser.
Therefore, when we had to output our content with a different header we had to make sure that it is done before PHP does it automatically. Two headers cannot be valid.
This is it for this post, do check back soon for more new posts. Till then, good bye!
