Sent to me by: Dedy Hisman
HIGHLIGHTS
* You can code yourself into an HTML mess with Python or PHP, but PHP
makes it more tempting.
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Server-side HTML Hell
By Nicholas Petreley
I once weighed Python against Java in a few ways that I hoped would not
rekindle the age-old Python versus Java wars. Now I intended to
introduce the topic of Python programming for web applications. But I
really can't do it justice unless I say a few words about an even
touchier duo than Python versus Java; Python versus PHP, or Hypertext
Pre-Processor.
Whether you are a fan of Python, PHP, or both, you're bound to react to
this introduction with disbelief, wondering why I would be foolish
enough to make such an apples to oranges comparison. But it isn't
really that odd if you consider that Python Server Pages (PSP) work
pretty much the same way as PHP. Python Server Pages allow you to
intertwine HTML with Python. The PHP language is also integrated with
HTML into executable pages. The programming philosophy is basically the
same in either case.
The strength of PSP and PHP, as well as with the other server page
approaches like JSP and ASP, is that you get to crank out HTML and
program code at the same time. The weakness is that you get to crank
out HTML and program code at the same time.
Good applications have three layers; presentation layer, data layer,
and application logic layer. It's bad enough that people usually don't
expend the effort to separate the data layer from the application layer
when they write code. It's even worse when you have the presentation
layer (HTML) so tightly integrated with your program's logic. It
usually leads to a mess that is difficult to maintain. And that is what
I don't like about PSP or PHP.
The difference between PHP and Python as languages is that it is more
natural not to integrate HTML with Python. I'll get into more detail
next week, but there are ways to program web applications in Python the
same way you would program any other application in Python. This
approach tends to free you from the kind of twisted HTML hell that PHP
often encourages. And it usually leads to a more modular approach to
building web applications.
Before you PHP fans go off on a rant, allow me to point out that HTML
hell is not a necessary consequence of using PHP. It is simply the
usual result, at least based on the PHP code I've looked at including
but not limited to PHP-Nuke. If you are willing to put in the effort,
you can write quite elegant code, even object-oriented code, using PHP.
The problem is that it is so easy to integrate PHP with HTML that it is
difficult to resist the temptation to crank out sloppy modules that
work immediately.
But the important point to take away from this is that this weakness is
tied to the server page model, not the language of PHP itself.
In case you PHP fans are still not satisfied, not only do I admire the
way PHP works, but my two web sites www.varlinux.org and
www.petreley.org are based on PHP-Nuke, which is written in (you
guessed it) PHP. So I like it enough to use it, and I learned what
little I know about PHP by refining these web sites and adding features
to the PHP-Nuke system.
In fact, I'm about to show you how I used PHP to add a couple new
features to PHP-Nuke. And the code takes as quick-and-dirty an approach
as I'm advising you not to follow. But one of the first rules of doing
anything is that quick-and-dirty isn't always something to be avoided.
Whipping up PHP
Consider this problem I wanted to solve for www.varlinux.org. Most of
the article links in the table of contents for VarLinux.org point to
items that are published on other sites. The title of each entry in my
table of contents is linked to the off-site article. This makes it easy
to jump right to the articles if they look interesting, since you don't
have to scan the comments for a link as you might do with similar
weblog sites.
The problem is that PHP-Nuke only keeps track of the number of times
someone looks at the comments associated with off-site articles. It
doesn't count the number of times people click on the link and visit
that off-site article.
So rather than link directly to the off-site article, I tossed together
a script that redirects the reader's browser to the off-site item.
Before it does the redirection, it increments the counter for that
article in the database.
Now all the titles in the table of contents point to the redirect
script instead of the off-site link. The redirection happens "behind
the scenes" and runs in an instant so the user doesn't see any
difference in the way the site behaves. But now I can find out which
articles people are reading and which ones they aren't.
Once I had the redirect script working, I tossed together a script that
lists out all the titles, hit counters and dates of the most recent
articles. This allows me to track the counter information that I am
collecting with the redirect script.
I didn't time myself, but it must have taken a maximum of about 15
minutes to put together both of these PHP scripts. PHP is that easy
once you get used to it. Next week I'll talk about the Python-based
alternatives to Python Server Pages and PHP. Python is harder to use in
this way than PHP, but the additional effort can really pay off.
EXAMPLES:
Here is a sample version of the redirect.php script. The database table
field storyurl contains the full URL to the off-site article, and the
field sid is the ID number for the article.
$result = mysql_query("SELECT storyurl FROM stories WHERE sid =
$op");
list($storyurl) = mysql_fetch_row($result);
mysql_free_result($result);
mysql_query("UPDATE stories SET counter = counter+1 where sid =
$op");
Header("Location: $storyurl");
In order to use it, you must create a link for each article like the
following:
redirect.php?op = sid
As I mentioned above, the variable sid is the story ID number for the
article to which users will be redirected.
Please note that this code will not work as is with PHP-Nuke. For one
thing, PHP-Nuke does not store the URLs for off-site stories in the
mySQL database, so you won't find the field storyurl anywhere in the
PHP-Nuke code. This is one of the modifications I made to PHP-Nuke and
the mySQL-based PHP-Nuke database.
For another thing, the theme function themeindex that presents the
links on the table of contents does not track the sid ID number by
default. I added the code to pass this value to the function.
Finally, here is the code I use to look at the article list to see
which articles people are reading most:
if ($admin) {
include("header.php");
$result = mysql_query("SELECT time, counter, comments, title, sid
FROM stories order by time DESC, counter DESC, title");
while(list($storydate, $storycounter, $comments, $storytitle,
$sid) = mysql_fetch_row($result)) {
echo " < tr>";
echo " < td>$storydate < /td>";
echo " < td align=right>$storycounter</td>";
echo " < td align=right>$comments</td>";
echo " < td> </td>";
echo " < td><a href = article.php?sid =
$sid>$storytitle</a></td>\n";
echo " < /tr>";
}
mysql_free_result($result);
include("footer.php");
} else {
Header("Location: index.php");
}
This is one example of how you can integrate HTML with PHP code. The
multiple lines of echo statements could have been merged into a single
line, but I separate them out for readability. It isn't the only way,
however. You can write plain HTML code in a PHP file and escape out of
it to write occasional PHP code.
In the above example, only the administrator gets to see this
information. If anyone else tries to look at this file, they will be
redirected to the table of contents (index.php).
Note that the code includes table rows and data fields without first
creating a table. That's because the table is initialized in the file
header.php which is "included" in this code and executed first. Then
the tables are closed and wrapped up in footer.php, which is included
last. This is the kind of arrangement that can lead to HTML hell in
your PHP code, and makes the code difficult to debug.
If you want to look at my modified version of PHP-Nuke, you can
download it from http://www.varlinux.org/download.php. Unfortunately, I
cannot support this forked version, and I can't even guarantee you can
start up a site with it, since I haven't modified all the installation
details. But it may help you to have a look at the code, anyway.
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ADDITIONAL RESOURCES
PHP
http://www.php4.org
Python
http://www.python.org
Sun Microsystems, Inc.
http://java.sun.com
VarLinux.org
http://www.varlinux.org
PHP-Nuke
The Future of the Web
http://www.phpnuke.org
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