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require_once 'prepend.inc';
commonHeader('PHP Tutorial');

	function example($text) {
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		highlight_string($text);
		echo "</td></tr></table></blockquote>";
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?>
<h1>Introductory Tutorial</h1>
PHP is a tool that lets you create dynamic web pages.
PHP-enabled web pages are treated just like regular HTML pages and you can create
and edit them the same way you normally create regular HTML pages.

<h2>What do I need?</h2>
In this tutorial we assume that your server has support for PHP activated and that all files
ending in <i>.php3</i> are handled by PHP.  On most servers this is the default
extension for PHP files, but ask your server administrator to be sure.  If your server supports
PHP then you don't need to do anything.  Just create your <i>.php3</i> files and put them in
your web directory and the server will magically parse them for you.  There is no need to
compile anything nor do you need to install any extra tools.  Think of these PHP-enabled
files as simple HTML files with a whole new family of magical tags that let you do all sorts of
things.

<h2>Your first PHP-enabled page</h2>
Create a file named <i>hello.php3</i> and in it put the following lines:
<?example('<html><head><title>PHP Test</title></head>
<body>
<?php echo "Hello World<P>"; ?>
</body></html>
')?>
The colours you see are just a visual aid to make it easier to see the PHP tags and the
different parts of a PHP expression.  Note also that this is not like a CGI script.  The
file does not need to be executable or special in any way.  Think of it as a normal HTML
file which happens to have a set of special tags available to you that do a lot of
interesting things.<P>
This program is extremely simple and you really didn't need to use PHP to create a page
like this.  All it does is display: <B>Hello World</B><P>
If you tried this example and it didn't output anything, chances are that the server you
are on does not have PHP enabled.  Ask your administrator to enable it for you.<P>
The point of the example is to show the special PHP tag format.  In this example we used
<b>&lt;?php</b> to indicate the start of a PHP tag.  Then we put the PHP statement and
left PHP mode by adding the closing tag, <b>?&gt;</b>.  You may jump in and out of PHP
mode in an HTML file like this all you want.

<h2>Something Useful</h2>
Let's do something a bit more useful now.  We are going to check what sort of browser
the person viewing the page is using.  In order to do that we check the user agent string
that the browser sends as part of its request.  This information is stored in a variable.
Variables always start with a dollar-sign in PHP.  The variable we are interested in is
<b>$HTTP_USER_AGENT</b>.  To display this variable we can simply do:
<?example('<?php echo $HTTP_USER_AGENT; ?>')?>
For the browser that you are using right now to view this page, this displays:
<blockquote><?php echo $HTTP_USER_AGENT; ?></blockquote>
There are many other variables that are automatically set by your web server.  You can get a
complete list of them by creating a file that looks like this:
<?example('<?php phpinfo()?>');?>
Then load up this file in your browser and you will see a page full of information about PHP along with
a list of all the variables available to you.<P>

You can put multiple PHP statements inside a PHP tag and create little blocks of code that do
more than just a single echo.  For example, if we wanted to check for Internet Explorer we could
do something like this:
<?example('<?php
if(strstr($HTTP_USER_AGENT,"MSIE")) {
	echo "You are using Internet Explorer<br>";
}
?>');?>
Here we introduce a couple of new concepts.  We have an &quot;if&quot; statement.  If you are familiar with
the basic syntax used by the C language this should look logical to you.  If you don't know enough
C or some other language where the syntax used above is used, you should probably pick up any
introductory C book and read the first couple of chapters.  All the tricky string and memory manipulation
issues you have to deal with in C have been eliminated in PHP, but the basic syntax remains.<P>
The second concept we introduced was the strstr() function call.  strstr() is a function built into PHP
which searches a string for another string.  In this case we are looking for &quot;MSIE&quot; inside
$HTTP_USER_AGENT.  If the string is found the function returns true and if it isn't, it returns false.
If it returns true the following statement is executed.<P>
We can take this a step further and show how you can jump in and out of PHP mode even in the middle of
a PHP block:
<?example('<?php
if(strstr($HTTP_USER_AGENT,"MSIE")) {
?>
<center><b>You are using Internet Explorer</b></center>
<?
} else {
?>
<center><b>You are not using Internet Explorer</b></center>
<?
}
?>');?>
Instead of using a PHP echo statement to output something, we jumped out of PHP mode and
just sent straight HTML.  The important and powerful point to note here is that the logical
flow of the script remain intact.  Only one of the HTML blocks will end up getting sent to the
viewer.  Running this script right now results in:<P>
<?php
if(strstr($HTTP_USER_AGENT,"MSIE")) {
?>
<center><b>You are using Internet Explorer</b></center>
<?
} else {
?>
<center><b>You are not using Internet Explorer</b></center>
<?
}
?>
<h2>Dealing with Forms</h2>
One of the most powerful features of PHP is the way it handles HTML forms.  The basic concept that
is important to understand is that any form element in a form will automatically result in a variable
with the same name as the element being created on the target page.  This probably sounds confusing, so
here is a simple example.  Assume you have a page with a form like this on it:
<?example('<form action="action.php3" method="POST">
Your name: <input type=text name=name>
You age: <input type=text name=age>
<input type=submit>
</form>');?>
There is nothing special about this form.  It is a straight HTML form with no special tags of any kind.
When the user fills in this form and hits the submit button, the <i>action.php3</i> page is called.  In this
file you would have something like this:
<?example('Hi <?php echo $name?>.  You are <?php echo $age?> years old.')?>
It should be obvious what this does.  There is nothing more to it.  The $name and $age variables are
automatically set for you by PHP.
<h2>More?</h2>
This tutorial will get expanded, but at this time this is all there is.  With what you know now
you should be able to understand the online manual and also the various example scripts available
in the example archives.
<P>
Here is a list of other excellent PHP tutorials:
<ul>
<li><a href="http://www.hotwired.com/webmonkey/99/21/index2a.html">WebMonkey</a>
<li><a href="http://www.devshed.com/Server_Side/PHP/Introduction/">DevShed</a>
<!-- site is down as of 7/8/1999
<li><a href="http://www.314interactive.com/io/content.php3?sec=art&req=mysql&issue=4&pg=1">ionline</a>
-->
<li><a href="http://www.htmlwizard.net/resources/tutorials/">phpTidbits</a>
<li><a href="http://www.phpbuilder.com/getit/">PHP Builder</a>
</ul>

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