by December 31, 2000 0 comments

PHP is a server-side scripting language like CGI, ASP, and
Java Servlets. It’s easy to use and borrows its syntax from popular
programming languages like C, C++, and Java. It’s available for a number of
platforms and Web Servers like Apache on Linux and IIS (Internet Information
Server) on Win NT and 2000. It can be used in conjunction with many RDBMS. In
this article we’ve used it with MySQL. MySQL is a robust RDBMS database that’s
available for both Linux and Windows. In this article we’ll set up PHP 4 on
Apache Web Server and MySQL on a PCQ Red Hat system. We’ll then use PHP to
publish the data in a MySQL database on the Web. So let’s get started.

Setting up MySQL and PHP 4

Log in as root. Ensure that you have apache installed on your
machine with the apache development libraries. Check this by using the following
command:

rpm -qa | grep apache

If you see two RPMs named apache and apache-devel, then we
are ready to sprint, else change to the RPMs directory of the PCQ Red Hat CD and
install the two RPMs as:

rpm -ivh apache*

Next mount this month’s PCQ CD and change to the directory
/mnt/cdrom/cdrom/linux/mysql and install MySQL RPMs:

rpm -ivh MySQL*

Then as recommended during installation, change the password
of the root user:

mysqladmin -u root password pcq

Here we have changed the password to ‘pcq’.

Now we’ll set up PHP 4. Change to the directory /mnt/cdrom/cdrom/linux/php4
and copy the file php-4.0.3pl1.tar.gz to any directory say /opt. Change to /opt
directory and type the following to uncompress and extract PHP files:

tar -zxvf php-4.0.3pl1.tar.gz

This would create a directory named php-4.0.3pl1 in /opt.
Change to this directory and issue the following commands:

./configure –with-mysql –with-apxs

make

make install

This would install the PHP 4 module for apache. Now edit the
file httpd.conf in /etc/httpd/conf directory and add the following line in the
end:

AddType application/x-httpd-php .php

This defines the MIME type of PHP script files to Apache. In
other words, it tells Apache that any file with a PHP extension must be treated
as a PHP script and given to the PHP parser, which would analyze and execute the
PHP scripts.

Now restart Apache Web Server:

/etc/rc.d/init.d/httpd restart

At this point if you get an error message saying, ‘cannot
load /etc/httpd/lib/apache/libphp4.so’, then edit the file httpd.conf again
and look for a line which says:

LoadModule php4_module
lib/apache/libphp4.so

Replace lib/apache/libphp4.so to modules/libphp4.so, so that
the line looks like:

LoadModule php4_module modules/libphp4.so

Restart Apache once again.

Testing the setup

We’ll now write a simple script to test if everything is up
and running. This php script just tries to connect to the MySQL server.

In the directory /home/httpd/html, create a file test.php and
enter the following:

PHP and MySQL test

$connection=mysql_connect (“localhost”,”root”,”pcq”);

echo “A simple test”

?>

Note that this file seems to be a normal HTML file due to the
presence of familiar HTML tags. But the extension of the file (PHP) instructs
Apache to invoke the PHP parser. The PHP parser sends all lines, except the
lines between . The lines between these tags are processed by
the PHP parser. The first line between these connects to the MySQL server
running on the same machine (specified by local host), using the username ‘root’
and password ‘pcq’.

Next fire up your browser, say Netscape Navigator or Lynx and
feed in the URL http://localhost/test.php. If you see the message ‘A simple
test’ and no error messages then everything is setup properly. However, if you
do see an error message, like ‘MySQL connection failed’ then make sure that
the MySQL server is running by using the following command:

/etc/rc.d/init.d/mysql start

Publishing a database

From
here, we’ll assume that you’re familiar with SQL queries. Suppose we are
running an e-commerce site, which maintains a list of products along with their
product ID and price in a table named ‘info’, which is in a database named
‘products’. We’ll first have to create the database by typing the
following at the shell prompt:

mysqladmin create products -p

You’ll be prompted for the password (pcq) and subsequently
the database would be created.

Now type:

mysql -p

Enter the password again. You’ll get a mysql prompt. Next
type the following at the mysql prompt:

use products;

create table info (id char(10) NOT NULL, product char(20),
price float, PRIMARY KEY id);

This creates a table named info with fields: id, product (the
products name), and its price (say in Rs). The next step is to populate this
table with information. For example, to enter information about an Apple iMAC
computer issue the following while still in the mysql prompt:

insert into info values ("0123456789","Apple iMac",80000.00);

Repeat this line for inserting some more products, each time
replacing the information in the brackets ( ). Now exit from MySQL by typing
quit and create a file named product.php in the /home/httpd/html directory and
add the following linest:

<html>

<head>

<title>Product Information</title>

</head>

<body>

<h1 align=center>Product Information</h1>

<table border=1 align="center">

<tr>

<th>Product ID</th>

<th>Product</th>

<th>Price (in Rs)</th>

</tr>

<?php

$connection = mysql_connect("localhost","root","pcq");

mysql_select_db("products",$connection);

$query_result = mysql_query("select * from info");

while ($row = mysql_fetch_array($query_result))

{

echo "<tr>";

echo "<td>";

echo $row["id"];

echo "</td>";

echo "<td>";

echo $row["product"];

echo "</td>";

echo "<td>";

echo $row["price"];

echo "</td>";

echo "</tr>";

}

?>

</table>

</body>

</html>

Let’s throw some light on the lines between the <?php
and ?> tags. First, a connection to the server is made. Then in the second
line, the MySQL database named ‘product’ is selected. Now we are ready to
query the database. This is done by the PHP function mysql_query ( ), where we
select all the information stored in the table ‘info’. The mysql_query( )
can execute any SQL query like we could also create tables as well as insert,
delete, or modify the information in them.

The result of the query is stored in a variable named
query_result. This variable contains a two dimensional array of row by row
information extracted from the query. Thus we iterate through this variable
using a while loop. At each iteration one row is fetched and stored in the
variable $row. The individual elements are then extracted using the name of the
field, which are ‘id’, ‘product’, and ‘price’.

Now open the URL, http://127.0.0.1/product.php. You will see
the product information in a tabular format and this page has been created
dynamically by PHP by looking into the MySQL database. PHP can also connect and
query other databases like Oracle, MS SQL Server, or any other ODBC database
like Access, etc. Only the corresponding PHP functions differ like mssql_query(
), odbc_connect. PHP has extensive documentation, which is also given on this
month’s CD for your reference.

Shekhar Govindarajan

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