Find out how to script in PHP, an open-source
embedded scripting language for HTML. You'll learn how to install and
configure PHP for use with the Apache Web server on UNIX or the
Microsoft Internet Information Server on Windows NT.
Script Web Databases Quickly with PHP Scripting Language
Flexible open-source tool works with seven databases
Find out how to script in PHP, an open-source embedded scripting
language for HTML. You'll learn how to install and configure PHP for
use with the Apache Web server on UNIX or the Microsoft Internet
Information Server on Windows NT. Then you'll see by example how to use
PHP to route HTML conditionally, to develop a simple database-driven
Web application, and to track user sessions with cookies.
Like Microsoft's Active Server Pages (ASP), PHP is a server-side
scripting language for building Web sites. With strong tools for
working with more than ten commercial and noncommercial databases, PHP
may be the ideal tool if you often rely on databases in your Web
development -- and especially if you develop for both NT and for UNIX.
If you're ready to try such a flexible open-source tool, read on for
details about scripting with PHP. For installation instructions, see
Installing PHP version 3 on Windows NT (with the MS Internet
Information Server) and Installing PHP version 3 on UNIX (with Apache).
What is PHP?
PHP is an HTML-embedded scripting language for Windows and UNIX
designed to help Web developers write dynamically generated pages
quickly. Much of its syntax is borrowed from C, Java, and Perl, so
developers familiar with those should feel comfortable with PHP right
away.
One of PHP's greatest strengths is its easy interface to a wide variety of databases. Current database modules include:
• Informix
• Microsoft SQL Server
• mSQL
• MySQL
• ODBC
• Oracle
• Sybase
Additionally, a large set of optional components (some of which require installing an external library) provide support for:
• Accessing LDAP servers
• Accessing IMAP mail servers
• Sending SMTP mail
• Accessing SNMP
• Generating PDF documents dynamically
• Generating GIF images dynamically
• Parsing XML documents
• Checking the spelling of words
• Generating WDDX (Web Distributed Data Exchange) data
A short history of PHP
Rasmus Lerdorf originally wrote PHP to manage his home page, hence the
name, an acronym for personal home pages. The product quickly gained a
following, and later a group of developers rewrote it as PHP 3. PHP
development continues today with a core team of developers that include
Lerdorf, Andi Gutmans, Zeev Suraski, Stig Bakken, Shane Caraveo, and
Jim Winstead.
The current version of PHP is version 3, but a new and faster version has been released this summer in beta. (See "PHP version 4 beta debuts.")
Simple scripting
Once you install PHP 3, you can try scripting a simple database to get a feel for how it works.
All the programming examples in this article work with both PHP 3
and the beta version of PHP 4. You can download the code examples; see
the Resources section of this article.
Standard PHP scripts begin with <?php. And they end with ?>. All PHP variables start with $ just like in Perl.
Also as in Perl, there's no need to declare variables before using
them. You embed all the PHP code within the HTML script, so you can use
your favorite text editor to edit PHP files. There's even optional
support for Microsoft's FrontPage.
You can switch between HTML and PHP scripting as much as you like
within a file. For example, note the PHP mixed with HTML in the code in
Listing 1, which shows how to create conditional HTML. The ereg
function in line 3 of the listing does regular-expression matching on
the browser identifier ($HTTP_USER_AGENT) looking to find "MSIE."
Note that the syntax of the if/else statement is identical to C's
syntax. For more information on PHP functions used in the example
listings, check the online PHP Manual (see Resources).
Listing 1. PHP embedded within HTML generates different Web content for users with Microsoft Internet Explorer
Listing 1
1 <HTML>
2 <?php
3 if ( eregi ( "MSIE", $HTTP_USER_AGENT ) ) {
4 ?>
5 You are using <B>Microsoft Internet Explorer</B>!
6 <?php
7 } else {
8 ?>
9 You are not using Microsoft Internet Explorer.
10 <?php
11 }
12 ?>
13 </HTML>
Switching between HTML and PHP is very handy, but it is sometimes
difficult to read. You could rewrite the script in Listing 1 more
legibly by using the print function, as shown in Listing 2.
Listing 2. This script performs the same function as Listing 1, but it's easier to read
Listing 2
1 <HTML>
2 <?php
3 if ( eregi ( "MSIE", $HTTP_USER_AGENT ) )
4 print ( "You are using <B>Microsoft Internet Explorer</B>!\n" );
5 else
6 print ( "You are not using Microsoft Internet Explorer.\n" );
7 ?>
8 </HTML>
Setting up the database
To keep this example simple on screen, the address book contains only
the person's first name, last name, and e-mail address. If you download
the sample code , though, you'll find additional fields that make the application more useful.
This example uses MySQL, but you could use any database that PHP
supports. If you use another database (such as Oracle or ODBC), you
will need to adapt the listing because PHP's API is slightly different
for each database. For example, for ODBC connections you would use
odbc_pconnect instead of connecting with the mysql_pconnect function.
Note that I've used MySQL's auto-increment feature in these
examples. It's a handy way to generate unique integer keys for a table
column. You can do the same thing with other databases by using stored
procedures and triggers.
First, you must set up a valid MySQL login and password to use PHP. See the MySQL documentation for details (see Resources).
Then use the SQL commands in Listing 3 to set up the PERSON table
within a database called ADDRESS_BOOK and add a single entry into the
database. Enter the text using the mysql command-line program that is
part of the MySQL distribution.
Listing 3. The commands for setting up the MySQL database and for entering the first contact
Listing 3
1 CREATE DATABASE ADDRESS_BOOK;
2
3 USE ADDRESS_BOOK;
4
5 CREATE TABLE PERSON (
6 ID int(10) DEFAULT '0' NOT NULL AUTO_INCREMENT,
7 LAST_NAME VARCHAR(50) NOT NULL,
8 FIRST_NAME VARCHAR(50) NULL,
9 EMAIL VARCHAR(60) NULL,
10 PRIMARY KEY ( ID )
11 );
12
13 INSERT INTO PERSON VALUES (
14 1, 'Knudsen', 'Craig', 'cknudsen@radix.net' );
Retrieving data
Next you create a directory for the application. A good place for this
would be /opt/apache/htdocs/addressbook for an Apache installation,
/opt/apache or C:\INETPUB\WWWROOT\ADDRESSBOOK for IIS. The default page
for the application will be index.php3; you must configure your Web
server to recognize index.php3 as the default page for a directory.
Listing 4 shows the code for index.php3, a script that generates an
index page of all entries in the database sorted by last name. Each
displayed name serves as a link to a page that allows users to view all
fields for the selected name.
Listing 4. PHP script indexes entries by last name
Listing 4: index.php3
1 <HTML><HEAD>
2 <TITLE>Address Book Index</TITLE>
3 </HEAD><BODY>
4 <H1>Address Book Index</H1>
5 <UL>
6 <?php
7 // Connect to database.
8 $c = mysql_pconnect ( "localhost", "mylogin", "mypasswd" ) ||
9 die ( "Error connecting to database!" );
10 // Get each entry sorted by name.
11 $res = mysql_db_query ( "ADDRESS_BOOK",
12 "SELECT * FROM PERSON ORDER BY LAST_NAME, FIRST_NAME" );
13 while ( $entry = mysql_fetch_array ( $res ) ) {
14 printf ( "<LI><A href=\"view.php3?id=%d\">%s, %s</A>\n",
15 $entry["ID"], $entry["LAST_NAME"], $entry["FIRST_NAME"] );
16 }
17 // Free resources.
18 mysql_free_result ( $res );
19 ?>
20 </UL>
21 <P><HR>
22 <A href="edit.php3">Add New Entry</A>
23 </BODY>
24 </HTML>
In Listing 4 (and in the other listings below), you replace mylogin
and mypasswd with the correct login and password for your MySQL
database. The first PHP command in Listing 4 is mysql_pconnect on line
8, which establishes a database connection. There is also a
mysql_connect function available. The mysql_pconnect command opens a
persistent database connection that remains open after the page
finishes processing. The subsequent request reuses the connection to
improve performance.
Opening a database connection often is the slowest step in a Web
application. Connections opened with mysql_connect automatically close
after the page finishes processing.
Line 11 of Listing 4 submits to the database an SQL query that asks
for all address book entries sorted by last name. A simple while loop,
in conjunction with mysql_fetch_array, retrieves each of the entries.
The C-style printf statement formats the output for each entry as a
link to view the entry. The ID column of each entry serves as a
parameter of the URL.
The $res result set variable returned from mysql_fetch_array is an
associative array. The values for each table column (LAST_NAME,
FIRST_NAME, etc.) are accessed using the name of the column.
Line 18 of Listing 4 frees the resources for the result set. You
need not explicitly free the result set, because PHP does that for you
automatically after the page is processed, but it's typically
recommended. In some applications, you issue a large number of queries
that could use up significant system resources if not they are not
freed during execution. (Note: PHP 4.0 automatically frees resources as
they are dereferenced.)
Form processing
Form processing under PHP is simple. Listing 5 and Figure 1 show an
example of a form for adding a new entry to the address book. A simple
table lines up the text-entry fields.
Listing 5. A script to create the form shown in Figure 1
Listing 5
1 <HTML><HEAD>
2 <TITLE>Address Book Edit</TITLE>
3 </HEAD><BODY>
4 <H1>Edit</H1>
5 <FORM ACTION="add_handler.php3" METHOD="POST">
6 <TABLE border=0>
7 <TR><TD><B>Last Name:</B></TD>
8 <TD><INPUT name="last_name" SIZE=30></TD></TR>
9 <TR><TD><B>First Name:</B></TD>
10 <TD><INPUT name="first_name" SIZE=30></TD></TR>
11 <TR><TD><B>Email:</B></TD>
12 <TD><INPUT name="email" SIZE=40></TD></TR>
13 </TABLE><P>
14 <INPUT TYPE="submit" VALUE="Save">
15 </FORM>
16 <P><HR>
17 <A href="index..php3">Back to Index</A>
18 </BODY></HTML>
The form in Listing 5 specifies the action add_handler.php3, which is shown in Listing 6.
Listing 6 introduces some new topics: form handling, adding new rows to a database, error handling, and redirecting.
The form contains three form elements in new.html : last_name,
first_name, and email. To access the value the user entered as the
last_name form element, the variable $last_name is used. In this
example, I submit the form using the HTTP post method. Use the same
technique when using get rather than post .
Line 7 of Listing 6 retrieves the value for the form element last_name, using the following logic:
1. Use the empty function to determine if the user left the last name blank. If so, then set $last_name to "NULL" .
Otherwise, use the addslashes function to add the appropriate
backslashes for quotes in the last name and place the last name in
double quotes. This prevents the script from submitting invalid SQL
requests to MySQL.
2.Conditional syntax just like that found in C, Perl, and Java
accomplishes the retrieval on lines 7 and 8. After processing the first
name and e-mail data in the same manner, line 14 creates the SQL INSERT
command to add the new entry to the database. There's no value for the
ID column because the AUTO_INCREMENT feature of MySQL was used to
create the PERSON table. The ID field automatically will have the next
available integer.
Line 16 sends the INSERT command to the database. If the request is
successful, it returns a positive value, and the user is redirected to
the index page index.php3 , using the redirect function on line 19.
(Note that the redirect function needs to be called before any HTML
output is sent.) The redirect causes processing of this page to end,
and an HTTP redirect header will be sent.
The script handles errors by saving the error message to the $error
variable, using the mysql_error function, and then not performing the
redirect. This allows the HTML at the end of the script to be
displayed. In the event of an error, lines 28 through 30 cause the
display of an error message and the SQL command that caused the
problem.
The downloadable version of the code example
includes some additional pages (editing and deleting entries). They do
not introduce any additional concepts, so they aren't included here in
the article.
Listing 6. Processing a submitted form
Listing 6
1 <?php
2 // Connect to database.
3 $c = mysql_pconnect ( "localhost", "mylogin", "mypasswd" ) ||
4 die ( "Error connecting to database!" );
5 // Add a backslash to all characters that would confuse SQL.
6 // Use NULL for values that were left empty.
7 $last_name =
8 empty ( $last_name ) ? "NULL" : "'" . addslashes ( $last_name ) . "'";
9 $first_name =
10 empty ( $first_name ) ? "NULL" : "'" . addslashes ( $first_name ) . "'";
11 $email =
12 empty ( $email ) ? "NULL" : "'" . addslashes ( $email ) . "'";
13 // Add new entry and redirect to index page.
14 $sql = "INSERT INTO PERSON ( LAST_NAME, FIRST_NAME, EMAIL ) ( " .
15 "$last_name, $first_name, $email )";
16 if ( ! mysql_db_query ( "ADDRESS_BOOK", $sql ) ) {
17 $error = mysql_error ();
18 } else {
19 Header ( "Location: index.php3" );
20 exit;
21 }
22 ?>
23 <HTML><HEAD>
24 <TITLE>Address Book Error</TITLE>
25 </HEAD><BODY>
26 <H1>Error</H1>
27 <?php
28 print ( $error );
29 if ( strlen ( $sql ) )
30 printf ( "<P><B>SQL:</B><BLOCKQUOTE><TT>%s</TT></BLOCKQUOTE>", $sql );
31 ?>
32 </BODY>
33 </HTML>
Maintaining sessions
HTTP cookies help track user sessions. For example, the first time a
visitor arrives at an online store a session is created. The script
then uses the session identifier any time the site needs to store
information about the user, such as adding a purchase to an online
order. Every request the browser makes to the server then includes the
session-identifier cookie, which allows the application to identify the
user associated with each request.
You can configure cookies to expire at any specified date and time
or after a certain duration. Use the mktime function to generate an
expiration based on a specific date or the time function to get the
current date and time.
To generate a unique session ID, use the uniqid function. The
result will be unique so long as no two IDs are generated at the same
microsecond. The uniqid function can optionally be passed the user's IP
address to remove the chance of two users getting the same session
identifier.
Because cookies are sent as part of the HTTP header, generating a cookie must take place before any HTML is processed.
Listing 7: Generating a session ID that expires at the end of the session
Listing 7
1 <?php
2 // Generating cookies must take place before any HTML.
3 // Check for existing "SessionId" cookie
4 $session = $HTTP_COOKIE_VARS["SessionId"];
5 if ( $session == "" ) {
6 // Generate time-based unique id.
7 // Use user's IP address to make more unique.
8 $session = uniqid ( getenv ( "REMOTE_ADDR" ) );
9 // Send session id - expires when browser exits
10 SetCookie ( "SessionId", $session );
11 }
12 ?>
13 <HTML>
14 <HEAD><TITLE>Session Test</TITLE></HEAD>
15 <BODY>
16 Current session id: <?php echo $session ?>
17 </BODY></HTML>
The script starts by checking for an existing session cookie. All
cookies are stored in the $HTTP_COOKIE_VARS associative array. Only
when there is no existing session identifier will a new one be
generated.
The example in Listing 7 provides a session that lasts until the
user exits the browser. Listing 8 generates a session cookie that will
last until January 1, 2000.
Listing 8: Generating a session ID with a specific expiration date
Listing 8
1 <?php
2 // Generating cookies must take place before any HTML.
3 // Check for existing "SessionId" cookie
4 $session = $HTTP_COOKIE_VARS["SessionId"];
5 if ( $session == "" ) {
6 // Generate time-based unique id.
7 // Use user's IP address to make more unique.
8 $session = uniqid ( getenv ( "REMOTE_ADDR" ) );
9 // Send session id - expires on Jan 1, 2000
10 SetCookie ( "SessionId", $session, mktime ( 0, 0, 0, 1, 1, 2000 ) );
11 }
12 ?>
13 <HTML>
14 <HEAD><TITLE>Session Test</TITLE></HEAD>
15 <BODY>
16 Current session id: <?php echo $session ?>
17 </BODY></HTML>
Rolling up your sleeves
Now that you've seen how to use MySQL and PHP to script Web sites, you
have the tools to quickly and efficiently build a database-driven Web
site of your own.
Because PHP is an open-source project, product support might not be
what you're accustomed to with a commercial product. However, a number
of online resources support developers, including FAQs and a
developer-supported annotated online manual. If you run into trouble,
you might want to start with the FAQs or the PHP support page.
Installing PHP version 3 on Windows NT
o install and run PHP, in addition to NT you need Microsoft IIS 4,
currently distributed as part of the NT 4.0 Option Pack. You also need
a database that's compatible with PHP; I use MySQL for the example
listings.
Download the latest binary distribution of PHP version 3 for Win32
(see Resources, at the end of this sidebar). I used PHP 3.0.6 for the
example listings in the article, and the distribution file was
php-3.0.6-win32.zip. Any 3.x version will work fine for the example
listings.
Unzip the zip file into a new directory, such as C:\PHP3.
In the new directory, rename the php3.ini-dist file to php3.ini and edit it with a text editor.
If this is your first time using PHP, you can leave most of the
default settings in the .ini file unchanged. You do need to enable one
of the database extensions so that PHP can communicate with a database.
To follow the examples in the article, choose MySQL, which is readily
available for Windows NT and many versions of UNIX. Enable MySQL by
removing the semicolon the starts the line extension=php3_mysql.dll.
When you're finished editing, save a copy of php3.ini in your
operating system directory, C:\WINNT. (Be careful if you have used
Notepad, which always saves files with the .txt extension.)
Next, you need to edit the NT registry. (Warning: If you damage the
registry, you can cause major system problems. Make sure you have
backed up before you edit the registry.)
1. From Windows, select Start>Run and type regedit to start the registry editor.
2. Go to the entry for HKEY_LOCAL_MACHINE:System:CurrentControlSet:Services:W3Svc:Parameters:ScriptMap.
3. Choose Edit >New >String Value.
4. In the highlighted area under Name, type .php3 and then press Return.
5. Double-click on the same highlighted area.
6. In the Edit String box that pops up, enter the value C:\PHP3\PHP3.EXE and then click OK.
Next you need to start up the Microsoft Management Console.
1. From Windows, choose Start>Windows NT 4.0 Option
Pack>Microsoft Internet Information Server>Internet Service
Manager.
2. Right-click the name of the Web server and select Properties from the menu that opens.
3. Click the Home Directories tab and select Script under Permissions.
4. Click Configuration. In the Application Configuration pop-up window that appears, select Add
5. Enter C:\PHP3\PHP.EXE %s %s for Executable, .php for Extension in the popup window.
6. Make sure that Script Engine is enabled.
7.Click OK to close the Add/Edit Application Extension Mapping window.
8. Click OK in the Application Configuration window.
9. Restart the IIS server.
Now that you've installed PHP, it's a good idea to test that it's working.
1. Enter a test script, such as the one in Win NT Installation Listing 1.
2. Save the script where your browser can access it. For example, you can put it in C:\INETPUB\WWWROOT\PHP\TEST.PHP3.
3. Open a browser.
4. Access the test script from your browser. In the example, you
can access the script with the URL http://localhost/php/test.php3.
Listing 9. A simple script to confirm successful installation on Win NT
Listing 9
<HTML>
<?php phpinfo(); ?>
</HTML>
Installing PHP version 3 on UNIX
To begin installation, you need to first assemble the software you
need. including Apache 1.3.x, if you don't already have it installed
(see Resources at the end of this sidebar). For this article, the
distribution file was apache_1.3.6.tar.gz. Also download the source
code for PHP version 3.. For this article, I used the PHP distribution
file php-3.0.9.tar.gz, but any 3.x version will work. You also need a
database that's compatible with PHP; I use MySQL for the example
listings.
Put the files apache_1.3.6.tar.gz and php-3.0.9.tar.gz in the same
directory. The /tmp directory is a good place, if you have sufficient
space on that partition. (I needed 38MB to build Apache and PHP under
Linux.)
Next you configure, build, and install in /opt/mysql a PHP-enabled
Apache Web server that can access a MySQL database by entering the
commands in UNIX Installation Listing 1.
PHP version 4 debuts in beta
Listing 10. Commands for installation and configuration on UNIX
1. gunzip -c
2. gunzip -c
3. cd apache_1.3.6
4. ./configure --prefix=/opt/apache
5. cd ../php-3.0.9
6. ./configure --with-mysql=/opt/mysql
--with-apache=../apache_1.3.6 --enable-track-vars
--with-config-file-path=/opt/apache/conf
7. make
8. make install
9. cd ../apache_1.3.6
10. ./configure --prefix=/opt/apache --activate-module=src/modules/php3/libphp3.a
11. make
12. make install
Lines 4 and 10 call for Apache to be installed in /opt/apache
rather than the default location of /usr/local/apache. Line 6 instructs
PHP to build with MySQL, which assumes that you have installed MySQL
into /opt/mysql rather than the default /usr/local/mysql. You can build
with support for other databases drivers, but the examples in this
article call for MySQL. Type configure --help to see the command-line
options needed to add support for the other database software.
Once Apache has been installed, you edit the httpd.conf file. If
you installed Apache in /opt/apache as shown in the listing above, the
configuration file will be /opt/apache/conf/httpd.conf.
In the configuration file, uncomment the line AddType application/x-httpd-php3 .php3.
Note: With PHP version 4 now available in beta release, the PHP
authors are encouraging developers to switch from using the file
extension .php3 to .php instead. To use the .php extension, add an
additional line in the configuration file that says AddType
application/x-httpd-php3 .php. (Note that the files distributed in the
demo use the php3 extension.)
Now it's time to start the server. If you installed according to my
instructions, use the command /opt/apache/bin/apachectl start.
See your operating system's documentation to find out how to start
Apache automatically at boot time, as the method varies widely among
the different versions of UNIX.
The first beta release of PHP version 4 occurred in July. PHP4 uses
the Zend scripting language engine, a complete rewrite of the scripting
engine for PHP. Although Zend currently is used only with PHP4, Zend
eventually will be used as the scripting engine for products other than
PHP.
The most ambitious goal of this major update is to improve
performance. Preliminary benchmarks performed by the PHP/Zend
developers show PHP 4.0 outperforms PHP 3 by a factor of five or more
on most applications. The same benchmarks also show that PHP 4.0
compares favorably to ASP's performance.
PHP4 includes a number of other improvements. The new features of PHP4 include:
• A full-featured debugger, with breakpoints and step-through execution.
• Accessing COM objects, which are abundant for Windows.
• Output buffering to allow you to abort the page in the middle of the script and send a redirect header instead.
• Automatic resource deallocation, which means that there's no need
to remember to free resources in PHP4 because they're deallocated soon
as they are no longer referenced.
• A new foreach loop.
• Boolean terms true and false are predefined.
• Reference support, much like C-style pointers, so that you can
use $foo = &$a to make $foo and $a two names to the same variable.
In August, developer Zeev Suraski indicated that PHP 4.0 would most
likely be released in November or December. However, the schedule is
subject to change based on feedback from the beta releases. As an
open-source project, it will be released when the developers decide the
product is ready.
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