PHP seems very much in vogue now — with most web hosts providing support for it. For those who have only vaguely heard of it and are not too sure what it is, this article discusses PHP and informally compares writing PHP scripts with writing CGI scripts in Perl.
PHP is a free server side scripting language. It can be built into web servers like Apache and you can use it to generate your pages dynamically. You will probably use it in situations you would have otherwise used a Perl CGI script for. For example, the PHP feedback form generated by thesitewizard.com's Feedback Form Wizard can be used by visitors to your website to send feedback to you.
This article was written in 2000 and compares two programming languages for the purposes of introducing PHP. As such, to understand it, you need some programming background. When I first wrote the article, a lot of the webmasters that visited thesitewizard.com knew Perl, and it was from that perspective that this article was written. This is of course no longer true today; nowadays, the majority of webmasters are probably not even remotely connected to the computer industry (except that they own websites). If you are not a programmer, you should probably read the article What is HTML? What are PHP and Perl? instead, since it was written with the layperson in mind.
It uses typeless variables the way Perl does, prefixed with a "$" sign and holding any data type you wish. For example, $whatever can be a variable that you can use to contain strings, numbers, whatever. If $whatever contained a number, you can increment its value using
Unlike Perl, which is a general purpose scripting language that you can use for a wide variety of purposes (and not just generating web pages), PHP was designed from the ground up to be used for scripting web pages. As a result, it has lots of facilities built into that you may have to write yourself or use some pre-written module if you were using Perl.
For example, do you want to send email to yourself from a form on the web page? In Perl, one common way to do this is to use code like the following:
open ( MAIL,"|/usr/sbin/sendmail -t"); print MAIL "To: myself\@example.com\n" ; print MAIL "From: visitor\@example.com\n" ; print MAIL "Subject: Comments from Web Form\n\n" ; print MAIL $mainmessage ; close ( MAIL ) ;
In PHP, the same thing would be coded as follows:
mail ( "firstname.lastname@example.org", "Comments from Web Form", $mainmessage, "From: email@example.com" );
Nifty, huh? The same goes for other facilities like sending or retrieving a document via HTTP or FTP, etc. Since PHP was specially designed for a website, the facilities that web designers typically want in a scripting language are built into it.
Another convenience is its handling of form input. Take for example a form with a field like:
The data submitted for that field is made available to your script in the array variable $_REQUEST['dateofbirth']. You can assign its contents to any variable you like, or use it directly. There's no need to parse form inputs or the like. All fields in the form are automatically converted to variables that you can access.
Accessing databases is just as easy. There are built-in facilities in PHP to access MySQL, MSQL, Dbase, Oracle, InterBase, and so on (the list is very long). Need to MIME encode your message? There's a function to do it for you too.
There are many more features. I obviously can't run through the entire list — it would take a whole book to be exhaustive. This is just to whet your appetite.
By default anything you type in your PHP document is given verbatim to the web browser. So a simple PHP script might look like the following:
<html> <head><title>My First PHP Script</title></head> <body> <h1>My First PHP Script</h1> <p> Welcome, Internet user from IP address <?php echo $_SERVER['REMOTE_ADDR']?>. Hope you like my first PHP page. </body> </html>
Notice that it looks exactly like a web page, except for the
<?php ... ?> bit,
which encloses the PHP script. In this case, all we want is for the script to output
the visitor's IP address to the page, hence we use the "echo" function. The web server's
REMOTE_ADDR is automatically made available to the PHP script via an
$_SERVER['REMOTE_ADDR']. In fact, all server environment variables are
available to the PHP script in the
$_SERVER array variable. So, for example, the name of your
visitor's browser is available in
There are many ways to embed your PHP script into your page, or to design your page itself. But you've probably already got the general idea. As I said, PHP was designed for web pages, so the idea of output to the server is built into its design. It makes writing such scripts a very pleasant task.
While I obviously enjoy using PHP as my web scripting language, I do not claim that it is the perfect solution for all your website needs.
You might want to consider the following prior to committing yourself to it. The list, incidentally, is not exhaustive.
Not all web hosts provide PHP facilities. Most do nowadays, however, so if yours does not, it's simply a matter of changing web hosts to one that does.
Like all web scripting languages (Perl included), debugging the script can be a pain in the neck unless you download and install your own copy of PHP. Otherwise you might spend many hours online trying to test and debug your script (unless of course it's a trivial script). Instructions for how to install it on Windows can be found in my article How to Install and Configure PHP 5 to Run with Apache on Windows at http://www.thesitewizard.com/php/install-php-5-apache-windows.shtml
Incidentally, you can also operate your own Apache web server at home, so as to mimic the entire environment of your actual site (or as close to it as necessary). You can read all about setting up your own Apache, if you have a Windows machine, from my other articles:
Of course if you have a Linux box around, you're probably all set. Just dig up your installation CDROMs and install the server and PHP module from there if you've not already done so. (Most modern Linux distributions come bundled with the Apache server and PHP Apache module.)
It is not a general purpose language. While it has many facilities specifically catered towards web programming, it is not Perl (or C or C++ or Java). I personally however find PHP more than adequate for my web programming needs.
It probably cannot beat Perl in terms of convenient and efficient text crunching. Let's face it: Perl is designed with crunching text in mind and has facilities for handling strings and the like that put most other languages to shame. However, PHP does have adequate facilities for most web purposes.
Most, if not all, of the Unix web hosts listed on thefreecountry.com's Budget Web Hosting have PHP support. You can find them at http://www.thefreecountry.com/webhosting/budget1.shtml
There are probably a few hosts listed on the Free Web Hosts with PHP Access pages that support PHP. You can check them out yourself at http://www.thefreecountry.com/webhosting/freewithphp.shtml if you don't want to pay for web hosting; note however that most free hosts disable certain PHP functions (like the mail() function) due to abuses.
The entire PHP documentation set comprising the reference manual for the various PHP language features and functions can be downloaded from the PHP web site at http://www.php.net/. The sources and binaries for PHP can also be found on the same site should you wish to run a copy on your own machine for testing purposes.
If you're interested in getting started with PHP, you might want to check out the following tutorials found on thesitewizard.com:
PHP Tutorial 1: Writing Your First PHP Script: Feedback Form
PHP Tutorial 2: Form Validation, Disabling Browser Caching, Embedding HTML Code
By the time you read this, there'll probably be other instalments of this PHP tutorial series. You might want to check up the main index of PHP articles yourself, at http://www.thesitewizard.com/php/index.shtml
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