The PHP scripting language (get it Here) will read, interpret
and act on input from the user. Generally the php scirpt will output some to let you
know it got the message and processed it. PHP has to be installed on the server
hosting your website (see this). If you have a
website being hosted or are considering it, make sure they support PHP or none of your
php scripts will work (I'll capitalize PHP when I'm taking about the language itself
and use lower case when referring to scripts).
Use the same editor to write your scripts that you use to edit HTML (I prefer vi, see
this to see why). You need plain text, no proprietary
formatting and no extra characters or symbols or anything else that might confuse php.
PHP has excellent on-line help resources on their website so use those as you work
with your scripts. Use indentation and comments foten and consistently so everything
is easy to read. you'll come later to edit the script and you'll need these as hints
to what you were doing and why.
You can name your scripts as some_script.php
if they are stand-alone scripts. If the script is within a web page then all you do is
use the <?php and ?> within the page. Whether this works
depends on modifying the Apache httpd.conf file (see below).
A PHP script begins by declaring itself:
<?php
and then turns itself off with:
?>
This is the same techique you're familiar with from HTML and also used throughout the
Apache configuration file (I'm going to assume you or your web host are using
Apache, preferrably version 2). To get PHP to work with Apache you will need to edit
the Apache configuration file, httpd.conf in the ServerRoot conf directory.
This is not a big deal, just these changes:
LoadModule php5_module modules/libphp5.so
<FilesMatch \.php$>
SetHandler application/x-httpd-php
</FilesMatch>
AddType application/x-httpd-php .php .php3 .phtml .html
You might also want to add a directive to Apache, (ExecCGI), to tell it to execute php scripts in
the top level directory for your web pages. This will allow you to run php scripts
within a web page:
<Directory "D:/Apache2.2/htdocs">
Options Indexes FollowSymLinks Includes ExecCGI
The <Directory ... > line is your DocumentRoot, the place where you keep your
web pages. You're telling Apache that it's ok to excute scripts inside the web pages in
this directory. The specific installation for both Apache and PHP for your operating
system is documented at the PHP web site. Make sure you follow those instructions to
ensure that everything is working right (See the documentation Here).
A php script is mostly a collection of functions. They are words followed by
parentheses:
function_name()
{
some php specific operations;
}
These functions can manipulate user input in various ways and then display the results
if you want. You can assign variables or use those created by PHP itself and there's
lots of ways to display output. In most case you will display the script's output to a
web page and PHP can create that page on-the-fly. PHP also creates a bunch of
variables that you can use in your scripts. The phpinfo(); function will show
all of them.
To create a php script:
<?php
$hello="Hello World!";
echo $hello;
phpinfo();
?>
Notice that the lines end with a semi-colon. I included the phpinfo(); line
so you can also see how PHP sets its own variables. The echo command can be repaced
by the print command but I prefer since I use it in shell scripts all the
time. The usual way you'll call a script is through a web form which means you will be
passing it the values the user filled in inside the form. The script will parse these
values and decide how to use them based on whatever you put in that script.
<?php
echo "
<center>
<form action=\"/name.php\" method=\"post\" name=\"postit\">
<input type=\"hidden\" name=\"feedback\" value=\"some_value\">
<p>Enter your name here:
<input type=\"text\" name=\"name\" \">
<input type=\"submit\" value=\" Add you name \">
</form>";
?>
Because the echo command is being used with the double quotes (") you will
have to escape any other double quotes with a backslash (\). The escaping of quotes is pretty much
standard in all programming languages. Notice that the script also outputs a string of
HTML code, this means that script both displays and interprets HTML. PHP can also call
itself within an HTML document so that it prompts for input within a HTML form, acts
on the input and displays HTML output all within the same page (Assuming that ExecCGI
was enabled in the Apache httpd.conf file).
All the form elements, "name=" create variables. When the form is submitted
those variables are passed to the php script where they are processed. Within the
script you can massage these variables in all kinds of ways and then, if you want,
store them in a file with whatever formatting you choose. This same script can also
echo back some HTML code to verify that the input was accepted (or not).
You can format this feedback as a complete web page with CSS, tables, more forms or
whatever you normally put in your web pages:
<?php
echo '
<html>
<head>
<title>
Feedback
</title>
<body>
<span style="font-family:verdana;font-size:11pt;">
<center>
<p>
<form action=comment.php method=post>
<table bgcolor="#eeeeff" cellspacing=10 border=5><tr><td>
<table background="images/cloth1.gif"><td><span style="font-family:verdana;">
.
.
.
Notice that this time I used the single quote ('). If you've got a lot of characters
requiring escaping, use the single quote and avoid the hassle; it will escape
(almost) everything for you. In this example an entire web page is being echoed back to the
user's browser. This means that the page you display from the php script can be
complete in every detail but with information specific to the current user. Since the
page is generated when the script is run, it doesn't exist on your website and that
means it takes up no disk space and it's one less file to upload or manage.
That's all I'm going to go into here since there's lots of really good tutorials on the Net already. My purpose here is only to show the virtues of PHP and how you can use it to
make your website more useful. PHP is easy to learn, just start with a simple form and
play with it.
