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Processing PHP output statements

stynak — Sun, 16 Mar 2008 08:09:38 +0000

The Hello World script, like most PHP scripts for the Web, is written mainly
to output HTML code that the browser then processes and displays in your
Web page. When writing PHP code to deliver output to a Web browser, you
need to keep in mind that there are two stages, as follows:
1. PHP processes the PHP statement and sends the output to the Web
server, which sends the output to the browser.
PHP does not know anything about HTML code and just sends the output
according to the instructions you write in the PHP output statement.
2. The Web browser receives the output from PHP, interprets it as HTML
statements, and displays a Web page accordingly.
The Web browser only understands HTML, not PHP code, so make sure
your PHP output is understandable to your browser.
Consider the echo statement from the Hello World script:
echo _

Hello World!

The echo statement says to output everything that is between the double
quotes (“). So, for this statement, the two stages are as follows:
1. When PHP processes the echo statement, it outputs the following:

Hello World!

PHP does not understand HTML, so it does not know that

is an HTML
tag and does not see

as any sort of instruction. It just outputs the
statement as text.
2. The Web browser receives the output, recognizes that

is an HTML
tag, and displays the output on the Web page according to the HTML
tags. You see the following on the Web page:
Hello World!
The HTML tags

and

indicate the beginning and end of a paragraph
and are interpreted by the Web browser, but not displayed on the
screen. To see what PHP sent to the browser, view the source by using
the selections on your Web browser menu. For instance, in Internet
Explorer 5.5, choose View➪Source. For this Web page, the source would
show the following:

Hello World!

Writing Your First PHP Script

stynak — Sun, 16 Mar 2008 07:09:00 +0000

It’s sort of a tradition that the first program you write in any language is the
Hello World program. You may have written a Hello World program in
HTML when you first learned it. If you did, it probably looked similar to the
following HTML file:

Hello World HTML Program

Hello World!

If you point your browser at this HTML program, you see a Web page that displays
the following output in the browser window:

Hello World!

Your first PHP script is a script that does exactly the same thing. The following
code is a PHP script that includes both HTML and PHP code and displays
Hello World! in a browser window:

Hello World Script

echo “

Hello World!

”
?>

If you point your browser at this script, it displays the same Web page as the
HTML script.

Don’t look at the file directly with your browser. That is, don’t choose File➪
Open➪Browse from your browser menu to navigate to the file and click it.
You must point at the file by typing its URL, as discussed in Chapter 2. If you
see the PHP code displayed in the browser window, instead of the output you
expect, you may not have pointed to the file by using its URL.

In this PHP script, the PHP section consists of the following code:

echo _

Hello World!

_
?>

The PHP tags enclose only one statement — an echo statement — that simply
outputs the text between the double quotes.

When the PHP section is processed, it is replaced with the output. In this
case, the output is as follows:

Hello World!

If you replace the PHP section in the HTML version of Hello World with the
preceding output, the script now looks exactly like the HTML program. If you
point your browser at either program, you see the same Web page. If you look
at the source code that the browser sees (in the browser, choose View➪
Source), you see the same source code listing for both programs.

Choosing a Web hosting company

stynak — Sat, 15 Mar 2008 14:39:01 +0000

A Web hosting company provides everything you need to put up a Web site,
including the computer space and all the Web site software. You just create
the files for your Web pages and move them to a location specified by the
Web hosting company.

About a gazillion companies offer Web hosting services. Most charge a monthly
fee, which is often quite small, and some are even free. Most of the free ones
require you to display advertising. Usually, the monthly fee varies, depending
on the resources provided for your Web site. For instance, a Web site with
2MB (megabytes) of disk space for your Web page files costs less than a Web
site with 10MB of disk space.

When looking for a place to host your Web site, make sure that the Web hosting
company offers PHP. Some do not. Also, make sure the company offers a
recent version of PHP. Web hosting companies may not offer a version that
has just been released, but they should upgrade their PHP fairly soon after a
new version is released.

Don’t consider a Web hosting company that offers only PHP 3. PHP 4.3.1 was
released in February 2003, so no Web hosting company should still be providing
PHP older than 4.3.1, especially because a security issue was discovered
in earlier versions and was fixed in PHP 4.3.1. Ideally, by the time you read
this, most Web hosting companies will be offering PHP 5.

Other considerations when choosing a Web hosting company include the
following:

Reliability: You need a Web hosting company that you can depend on —
one that won’t go broke and disappear tomorrow. And you want one
that has enough computer power and other resources to keep your Web
site up. A Web site with more down time than up time is pretty useless.
Hopefully, some research on the Web or among colleagues will identify
Web hosting companies whose reliability is not up to snuff.
Speed: Web pages that download slowly are a problem because users
will get impatient and go elsewhere. Slow pages may be a result of a Web
hosting company that started its business on a shoestring and has a
shortage of good equipment, or the problem may be a Web hosting company
that is so successful that its equipment is overwhelmed by new
customers. Either way, Web hosting companies that deliver Web pages
too slowly are unacceptable. In some cases, you can find sites that are
hosted at the Web hosting company and see the download speed for
these sites. Sometimes the Web hosting company’s Web site provides
some customer links, or the company’s salespeople may provide you
with this information.
Technical support: Some Web hosting companies have no one available
to answer questions or troubleshoot problems. Technical support is
22 Part I: Say Hello to the PHP Scripting Language
often provided through e-mail only, which can be acceptable if the
response time is short. Sometimes you can test the quality of the company’s
support by calling the tech support number, or test the e-mail
response time by sending an e-mail.
Domain name: Each Web site has a domain name that Web browsers use
to find the site on the Web. Each domain name is registered, for a small
yearly fee, so that only one Web site can use it. Some Web hosting companies
allow you to use a domain name that you have registered independently
of the Web hosting company, some assist you in registering
and using a new domain name, and some require you to use their domain
name. For instance, suppose your company’s name is Good Stuff and you
want your Web site to be named JanetsGoodStuff. Some companies allow
your Web site to be JanetsGoodStuff.com, but some require that your
Web site be named JanetsGoodStuff.webhostingcompanyname.com,
or webhostingcompanyname.com/~GoodStuff, or something similar. In
general, your Web site will look more professional if you can use your
own domain name.
Backups: Backups are copies of your Web page files and your database
that are stored in case your files or database are lost or damaged. You
want to be sure that the company makes regular, frequent backup copies
of your application. You also want to know how long it would take for
backups to be put in place to restore your Web site to working order
after a problem.

It’s difficult to research Web hosting companies from a standing start — a
search at Google for Web hosting results in over 4 million hits. The best way
to research Web hosting companies is to ask for recommendations from
people who have experience with those companies. People who have used a
hosting company can warn you that the service is slow or that the computers
are frequently down. After you have gathered a few names of Web hosting
companies from satisfied customers, you can narrow the list to the one that
is best suited and most cost-effective for your purposes.

You can ask for names from colleagues and friends. Also, people often ask for
recommendations for hosting companies on the PHP discussion lists. Many
people on the lists have experience using PHP with Web hosting companies
and are glad to provide recommendations or warnings. Because people often
ask this question, you may get all the information you need from the list
archives, which you can search at marc.theaimsgroup.com/.

Using an existing Web environment

stynak — Sat, 15 Mar 2008 14:34:42 +0000

When you use a Web environment set up by someone else, you don’t need
to understand the installation and administration of the Web site software.
Someone else — your company’s IT department, a commercial Web hosting
company, your next-door neighbor — is responsible for the operation of the
Web site. It’s their job to provide you with a working Web site, including PHP
if it’s required. Your job is only to write and install the Web site files.

To use an existing Web environment, you need the following information from
the Web site administrator:

The location of Web pages: For the world to see your Web site, the files
containing the Web pages must be in a specific location on the computer.
The Web server that delivers the Web pages to the world expects to find
the files in a specific directory. You need to know where that directory is
and have access to the directory.
The Web page installation process: You need to know how to install the
files. In most cases, you send the files via FTP to the proper location. FTP
(File Transfer Protocol) is a method of copying a file from one computer
to another on a network. In some cases, you may copy the files directly
or use other methods to install the Web pages. You may need a user ID
and password to install the files.
The name of the default file: When users point their browsers at a URL, a
file is sent to them. The Web server is set up to send a specific default file
when the URL points to a directory. Very often the default file is named
index.htm or index.html, but sometimes other names are used, such as
default.htm. You need to know what you should name your default file.
The PHP file extension: When PHP is installed, the Web server is
instructed to expect PHP statements in files with specific extensions.
Frequently, the extensions used are .php or .phtml, but other extensions
can be used. PHP statements in files that do not have the correct extensions
won’t be processed. You need to know what extension to use for
your PHP scripts.

One of the disadvantages of hosting your site in an existing Web environment
is that you have no control over your development environment. The administrators of the Web environment provide the environment that works best for them. For instance, PHP has a myriad of options that can be set, unset, or given various values. The administrators decide the option settings based on
their needs, which may or may not be ideal for your purposes. They probably
set up the environment for ease of maintenance, low cost, and minimal customer defections. You can’t change certain parts of your environment; you
can only beg the administrators to change it. They will be reluctant to change
a working setup because a change may cause problems for their system or
for other customers.

Establishing Your Web Environment

stynak — Sat, 15 Mar 2008 14:33:29 +0000

PHP for Web development runs in partnership with a Web server, as described
in Chapter 1. Thus, a Web site requires a Web server. To use PHP in your Web
site, the Web server must be able to exchange information with the PHP software, and, thus, PHP must be installed where the Web server can access it.
The Web site environment involves more than just a Web server and PHP on a computer. Here are a few other requirements:

The computer must be connected to the Internet.
The computer must have enough resources, such as disk space and
memory, to handle the expected Web traffic.
Other software, such as a database, may be required in the environment.

You may or may not be interested in setting up your own Web environment.
You may think that installing software is fun, or you may think it’s similar to
having the flu. If you want to install your own Web environment from scratch,
you can. You may even already have a Web site running on your own computer
and are just looking to add to its functionality by using PHP. If you don’t want
to install your own Web environment, you can use a Web environment installed
and maintained by someone else, such as the IT department at work or a
commercial Web hosting company. Perhaps you have an existing Web site at
a hosting company that you want to make more dynamic. You can use PHP in
either a Web environment of your own or one provided by someone else.

Another common development environment includes both your own Web
environment and one maintained by someone else. That is, it’s common for
developers to set up testing Web environments on their own computers where
they write and debug Web pages. Then, when everything is working correctly,
the Web pages are transferred to their Web site at work, maintained by the IT
department, or to a Web hosting company.

The following are some advantages of using someone else’s Web environment:

It’s easier than setting up your own: You just copy your Web pages onto
the other party’s computer, and that’s it. You don’t need to install any
software or hardware or resolve any computer problems. Someone else
handles that for you.
Less technical skill is required: You need to understand only Web languages,
such as HTML and PHP. You don’t need to know about Internet
connections, Web servers, computer administration, and other technical
things. Some people are very interested in these things, but some are not.

Previous versions of PHP

stynak — Sat, 15 Mar 2008 14:30:47 +0000

You should be aware of some significant changes in previous PHP versions
because existing scripts that work fine on earlier versions may have problems
when they’re run on a later version, and vice versa. The following are some
changes you should be aware of:

Version 4.3.1: Fixed a security problem in 4.3.0. It’s not wise to continue
to run a Web site using versions 4.3.0 or earlier.
Version 4.3.0: Included significant improvements to the CLI version of
PHP, which is now built by default when you compile PHP from source
code (described in Appendix A). You must disable its build with installation
options if you don’t want it to be built.
Version 4.2.0: Changed the default setting for register_globals to Off.
Scripts running under previous versions may depend on register_
globals being set to On and may stop running with the new setting. It’s
best to change the coding of the script so that it runs with
register_globals set to Off.
Version 4.1.0: Introduced the superglobal arrays. Scripts written using
the superglobals (described in Chapter 6) won’t run in earlier versions.
Prior to 4.1.0, you must use the old style arrays, such as
$HTTP_POST_VARS.

By the time you read this, it’s possible that everyone has updated to PHP 5.
However, some IT departments and Web hosting companies may not update
immediately. Keep the previous changes in mind when using older versions.

PHP 5

stynak — Sat, 15 Mar 2008 14:29:52 +0000

Most of the important changes in PHP version 5 don’t affect the coding or the
use of PHP. They affect the performance of PHP. The Zend engine (the magic,
invisible engine that powers PHP) has been significantly improved, and as a
result, scripts run faster and more efficiently.

The object-oriented programming features of PHP are a major focus of PHP 5.
Object-oriented programming is greatly improved over PHP 4. The creation
and use of objects runs much faster, many object-oriented features have been
added, and exceptions are introduced. Programmers who prefer objectoriented
programming will be much happier with PHP 5. (Object-oriented
programming is described in Chapter 9.)

With PHP 5, the names of the PHP programs changed. PHP for the Web is
called php-cgi; PHP CLI is called just php, as in php.exe on Windows. Both
are stored in the directory where PHP is installed. Prior to PHP 5, both programs were named php.exe, but stored in different subdirectories.

PHP 5 adds support for MySQL 4.1 and later. However, support for MySQL
is not included with PHP 5 by default. Support for MySQL 4.0 or MySQL 4.1
must be specified when PHP is installed. Prior to PHP 5, support for MySQL
4.0 and earlier was included automatically.

PHP 5 includes support for SQLite by default. SQLite provides quick and easy
methods for storing and retrieving data in flat files.

Keeping Up with Changes in PHP

stynak — Sat, 15 Mar 2008 14:28:46 +0000

PHP is open source software. If you have only used software from major software
publishers — such as Microsoft, Macromedia, or Adobe — you will find
that open source software is an entirely different species. It’s developed by a
group of programmers who write the code in their spare time, for fun and for
free. There’s no corporate office to call with questions. There’s no salesperson
to convince you of the wonders of the software. There’s no technical support
phone number where you can be put on hold.

Sounds like there’s no support for PHP, doesn’t it? Actually, quite the opposite
is true: An incredible amount of support is available. PHP is supported by the
developers and by the many PHP users. But you need to look for the support.
It’s part of your job as a PHP user and developer to search out the information
you need.

Open source software changes frequently, rather than once every year or two
as commercial software does. It changes when the developers feel it’s ready.
It also changes quickly in response to problems. When a serious problem,
such as a security hole, is found, a new version that fixes the problem may be
released in days. You don’t receive glossy brochures or see splashy magazine
ads for a year before a new version is released. If you don’t make the effort to
stay informed, you may miss the release of a new version or be unaware of a
serious problem with your current version.

Visit the PHP Web site often. You need to know the information that’s published
there. Join the mailing lists, which often are very high in traffic. When
you first start using PHP, the large number of mail messages on the discussion
lists brings valuable information into your e-mail box; you can pick up a lot by
reading those messages. And soon, you may be able to help others based on
your own experience. At the very least, subscribe to the announcement mailing
list, which only delivers e-mail occasionally. Any important problems or new
versions are announced here. The e-mail you receive from the announcement
list contains information you need to know.

So, right now, before you forget, hop over to the PHP Web site and sign up for
a list or two at www.php.net/mailing-lists.php.

Using PHP for database applications

stynak — Sat, 15 Mar 2008 14:27:04 +0000

PHP is particularly strong in its ability to interact with databases. PHP supports
pretty much every database you’ve ever heard of and some you haven’t.
PHP handles connecting to the database and communicating with it, so you
don’t need to know the technical details for connecting to a database or for
exchanging messages with it. You tell PHP the name of the database and
where it is, and PHP handles the details. It connects to the database, passes
your instructions to the database, and returns the database response to you.

Major databases currently supported by PHP include the following:

dBASE
Informix
Ingres
Microsoft SQL Server
mSQL
MySQL
Oracle
PostgreSQL
Sybase

PHP supports other databases as well, such as filePro, FrontBase, and
InterBase. In addition, PHP supports ODBC (Open Database Connectivity),
a standard that allows you to communicate with even more databases, such
as Access and IBM DB2.

PHP works well for a database-driven Web site. PHP scripts in the Web site
can store data in and retrieve data from any supported database. PHP also
can interact with supported databases outside a Web environment. Database
use is one of PHP’s best features.

Using PHP for Web applications

stynak — Sat, 15 Mar 2008 14:20:29 +0000

In the beginning, Web pages were static — they just presented documents.
Users went to Web sites to read information. Documents were linked together
so that users could easily find the information they sought, but the Web pages
didn’t change. Every user who arrived at a Web page saw the same thing.

Soon Web page developers wanted to do more. They wanted to interact with
visitors, collect information from users, and provide Web pages that were
customized for individuals. Several languages have developed that can be
used to make Web sites dynamic. PHP is one of the most successful of these
languages, evolving quickly to become more and more useful and rapidly
growing in popularity.

PHP is a server-side scripting language, which means that the scripts are executed
on the server (the computer where the Web site is located). This is different
than JavaScript, another popular language for dynamic Web sites. JavaScript
is executed by the browser, on the user’s computer. Thus, JavaScript is a clientside
language. Web servers and the interaction between servers and clients are
discussed in the section “PHP for the Web,” later in this chapter.

Because PHP scripts execute on the server, PHP can dynamically create the
HTML code that generates the Web page, which allows individual users to
see customized Web pages. Web page visitors see the output from scripts,
but not the scripts themselves.

PHP has many features designed specifically for use in Web sites, including
the following:

Interact with HTML forms: PHP can display an HTML form and process
the information that the user types in.
Communicate with databases: PHP can interact with databases to store
information from the user or retrieve information that is displayed to
the user.
Generate secure Web pages: PHP allows the developer to create secure
Web pages that require users to enter a valid username and password
before seeing the Web page content.

PHP features make these and many other Web page tasks easy.

PHP is only server-side, meaning it can’t interact directly with the user’s computer.
That means PHP can’t initiate actions based on the status of the user’s
computer, such as mouse actions or screen size. Therefore, PHP alone can’t
produce some popular effects, such as navigation menus that drop down or
change color. On the other hand, JavaScript, a client-side scripting language,

can’t access the server, limiting its possibilities. For example, you can’t use
JavaScript to store data on the server or retrieve data from the server. But
wait! You don’t have to choose. You can use JavaScript and PHP together to
produce Web pages that neither can produce alone. See Chapter 11 for details
on using JavaScript and PHP together.