Part 1: An Introduction to PHP
by David Gowans
Introduction
Up until recently, scripting on the internet was something which very few people
even attempted, let alone mastered. Recently though, more and more people have
been building their own websites and scripting languages have become more
important. Because of this, scripting languages are becoming easier to learn and
PHP is one of the easiest and most powerful yet.
What Is PHP?
PHP stands for Hypertext Preprocessor and is a server-side language. This means
that the script is run on your web server, not on the user´s browser, so you do
not need to worry about compatibility issues. PHP is relatively new (compared to
languages such as Perl (CGI) and Java) but is quickly becoming one of the most
popular scripting languages on the internet.
Why PHP?
You may be wondering why you should choose PHP over other languages such as Perl
or even why you should learn a scripting language at all. I will deal with
learning scripting languages first. Learning a scripting language, or even
understanding one, can open up huge new possibilities for your website. Although
you can download pre-made scripts from sites like Hotscripts, these will often
contain advertising for the author or will not do exactly what you want. With an
understanding of a scripting language you can easily edit these scripts to do
what you want, or even create your own scripts.
Using scripts on your website allows you to add many new ´interactive´ features
like feedback forms, guest books, message boards, counters and even more
advanced features like portal systems, content management, advertising managers
etc. With these sort of things on your website you will find that it gives a
more professional image. As well as this, anyone wanting to work in the site
development industry will find that it is much easier to get a job if they know
a scripting language.
What Do I Need?
As mentioned earlier, PHP is a server-side scripting language. This means that,
although your users will not need to install new software, you web host will
need to have PHP set up on their server. It should be listed as part of your
package but if you don´t know if it is installed you can find out using the
first script in this tutorial. If you server does not support PHP you can ask
your web host to install it for you as it is free to download and install. If
you need a low cost web host which supports PHP I would recommend HostRocket.
Writing PHP
Writing PHP on your computer is actually very simple. You don´t need any special
software, except for a text editor (like Notepad in Windows). Run this and you
are ready to write your first PHP script.
Declaring PHP
PHP scripts are always enclosed in between two PHP tags. This tells your server
to parse the information between them as PHP. The three different forms are as
follows:
<?
PHP Code In Here
?>
<?php
PHP Code In Here
php?>
<script language="php">
PHP Code In Here
</script>
All of these work in exactly the same way but in this tutorial I will be using
the first option (<? and ?>). There is no particular reason for this, though,
and you can use either of the options. You must remember, though, to start and
end your code with the same tag (you can´t start with <? and end with </script>
for example).
Your First Script
The first PHP script you will be writing is very basic. All it will do is print
out all the information about PHP on your server. Type the following code into
your text editor:
As you can see this actually just one line of code. It is a standard PHP
function called phpinfo which will tell the server to print out a standard table
of information giving you information on the setup of the server.
One other thing you should notice in this example is th
at the line ends in a semicolon. This is very important. As with many other
scripting and programming languages nearly all lines are ended with a semicolon
and if you miss it out you will get an error.
Finishing and Testing Your Script
Now you have finished your script save it as phpinfo.php and upload it to your
server in the normal way. Now, using your browser, go the the URL of the script.
If it has worked (and if PHP is installed on your server) you should get a huge
page full of the information about PHP on your server.
If your script doesn´t work and a blank page displays, you have either mistyped
your code or your server does not support this function (although I have not yet
found a server that does not). If, instead of a page being displayed, you are
prompted to download the file, PHP is not installed on your server and you
should either search for a new web host or ask your current host to install PHP.
posted on Jun 4, 2007
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