PHP5

 PHP 5

Introduction
PHP5 is the latest incarnation of PHP (PHP: Hypertext Preprocessor)—a programming language devised by Rasmus Lerdorf in 1994 for building dynamic, interactive Web sites. Since then, it's been evolving into a full-fledged language in its own right, thanks to the hard work of all the people who contribute to its development.

A sure sign that PHP is maturing as a technology is evidenced by its totally revamped and upgraded support for object-oriented programming (OOP) principles and improved support for XML. The Zend engine (the part that interprets and executes PHP code) now enables PHP5 developers to implement, among a host of other things, graceful application-wide error handling.

With all the new features and functionality that PHP5 provides, it's important for programmers to "upgrade" their understanding in order to best make use of this powerful Web scripting tool. And that's why it's important for you, the reader, to invest your time learning about the latest and greatest that the people developing PHP5 have to offer.

That's all well and good, but what exactly is PHP?

You know it's a language for writing computer programs, so the real question is "What sort of programs can you write with it?" In technical terms, PHP's main use is as a cross-platform, HTML-embedded, server-side Web scripting language. Let's take a moment to examine these terms:

1. Cross-platform: Most PHP code can be processed without alteration on computers running many different operating systems. For example, a PHP script that runs on Linux generally also runs well on Windows.

2. HTML-embedded: PHP code can be written in files containing a mixture of PHP instructions and HTML code.

3. Server-side: The PHP programs are run on a server—specifically a Web server.

4. Web-scripting language: PHP programs run via a Web browser.

This means you'll write programs that mix PHP code and HTML, run them on a Web server, and access them from a Web browser that displays the result of your PHP processing by showing you the HTML returned by the Web server. In other words, you can make your programs available for other people to access across the Web, simply by placing them on a public Web server.

You're probably already familiar with HTML (HyperText Markup Language)—it's the main language used to create Web pages, combining plain text with special tags that tell browsers how to treat that text. HTML is used to describe how different elements in a Web page should be displayed, how pages should be linked, where to put images, and so on.

Pure HTML documents, for all their versatility, are little more than static arrangements of text and pictures, albeit nicely presented ones. However, most of the sites you find on the Web aren't static but dynamic, even interactive. They can show you a list of articles containing a particular word in which you're interested, show you the latest news, even greet you by name when you log on. They enable you to interact, and present you with different information according to the choices you make.

You can't build a Web site like that using raw HTML, and that's where PHP comes in. What sort of things can you do with it? Well, you can program sites that

1. Present data from a wide variety of sources, such as databases, files, or even other Web pages.

2. Incorporate interactive elements, such as search facilities, message boards, and straw polls.

3. Enable the user to perform actions, such as sending e-mail or buying something.
            In other words, PHP can be used to write the sort of sites that those who regularly use the Web are likely to encounter every day. From search engines to information portals to e-commerce sites, most major Web sites incorporate some or all of these sorts of programming. Among other things in the course of this book, you'll use PHP to build

1. A simple, online text editor
:
2. A Web-based e-mail application

3. An object-oriented contact manager application

4. An object-oriented logging agent

So, PHP5 can be used for a diverse range of applications, from simple utilities such as a text editor to powerful Web applications such as the logging agent case study. This book equips you with the knowledge necessary to build any kind of Web site you want using PHP5. You'll learn some useful techniques along the way and perhaps pick up some ideas that you can incorporate into your own Web sites and applications.

Web scripting is certainly the mainstay of PHP's success, but it's not the only way to use the language. Command line scripting—using CLI (Command Line Interface), which was introduced in PHP4—is one of many popular applications of PHP. (CLI is covered in an appendix at the end of this book). Client-side graphical user interface application development using GTK (Gnome ToolKit) is another.

Why PHP?
One of the best things about PHP is the large number of Internet service providers (ISPs) and Web hosting companies that support it. Today there are hundreds of thousands of developers using PHP, and it's not surprising that there are so many, considering that several million sites are reported to have PHP installed.

You already know that PHP is a cross-platform technology and that once you've written your Web page, it's easy to get it up and running on our Web server, but how does PHP compare with other technologies out there? Well, comparing PHP with Perl is a bit tricky because they were designed for different things. PHP was specifically designed to rapidly create dynamic Web content; Perl was not. As a result, Perl can sometimes be a complicated language that can become prohibitive for users who want to create Web pages. Comparing PHP with ASP is a more balanced comparison, but then you have to pay for ASP, and ASP doesn't work well on a variety of platforms—it needs to be used on other proprietary platforms for which you also must pay.

You may ask, "Is there a downside to PHP?" In the past, PHP has been criticized for the way it handled a number of things—for example, one of its main stumbling blocks was the way in which it implemented object support. However, PHP5 has taken stock of the downfalls of its predecessors and, where necessary, has completely rewritten the way in which it implements its functionality. Now more than ever, PHP is a serious contender for large-scale enterprise developments as well as having a large, consolidated base of small- to medium-sized applications.
Chapter 1: Getting up and Running
Overview
PHP, which stands for HyperText Preprocessor, is widely used for creating programmed features for Web sites because it is easy to learn and also because PHP syntax is drawn from other widely used languages, making it familiar to many programmers. In this chapter we present a very brief history of PHP, and then discuss the nature of PHP as it relates to the Web.

Before you can get into the nitty-gritty of programming with PHP5, you need a clear understanding of how PHP programs work across the Web, and that obviously implies knowledge of the Web protocol called HyperText Transfer Protocol (HTTP). HTTP is the language or format for communications from browser to Web server and back, and is therefore fundamental to many aspects of PHP. HTTP gets some coverage in this chapter, and quite a bit more in Chapter 3.

You'll see how to properly setup PHP on a Linux server, and on a Windows server as well. PHP programs run in conjunction with Web pages, which in turn run (or are distributed by) Web server software (such as Apache or IIS), which in turn run on top of an operating system (such as Linux or Windows). Although it's not strictly necessary to know everything about network operating systems to build good PHP programs, there are many aspects of PHP that are controlled or affected by the Web server. If you're unfamiliar with server computers, Web servers, and the like, don't worry. You'll soon see how they work, and look at the requirements and process of installing basic Web server software.

This chapter leads you through installing PHP on a Red Hat Linux machine running Apache, and through installing PHP on a Windows 2000 machine running IIS. Just pick the one that's right for you.

You'll also examine the contents of the PHP configuration file php.ini with you, and test your PHP installation.

Obviously there's a lot of work for you in this chapter, so let's get started.

The Roots of PHP
PHP is a programming language designed to work with HTML, but unlike HTML, PHP has data processing capabilities. If you are familiar with HTML, you know that it is not really a programming language, but more of a rendering language—that is, HTML enables you to write Web pages using code that creates a pleasing (hopefully) display of text, graphics, and links within a browser. Although there are a few helpful features of HTML (such as the capability to cause a form submission), for the most part HTML does nothing programmatically. For example, there are no HTML commands that enable you to add two numbers together, or access a database.

If you remember the Web back in the early '90s, you may recall that early Web pages were made from HTML code written as plain text source files. When you made a connection to a Web site with your browser, the Web server software sent these plain text HTML files to be processed and rendered into Web pages. Your browser actually did the rendering process (and still does, to be sure), but if you clicked View⇨Page Source, you'd see the raw HTML code.

Javascript (and a few other almost unknown programming languages) improved the situation for Web designers in that it provided for programmatic functionality within Web pages. However, it was limited to programmatic functionality on the user's computer, not on the back-end (on the Web server), where all the really cool data processing and database access takes place. Practical Extraction and Reporting Language (PERL) was one of the first widely used languages for programming on the back-end, but has limitations of its own, such as an inability to be mixed in with HTML for easy in-page programming.

So where does PHP fit in with HTML? PHP began as PHP/FI, developed in 1995 by Rasmus Lerdorf from some Perl scripts he had created for tracking accesses to his online resume. Eventually, Rasmus wrote an implementation in C, released the source code to the public, and by the beginning of 1998 version 3.0 of PHP was released (written by Rasmus Lerdorf, Andi Gutmans, and Zeev Suraski), the first version that is very similar to the current releases of PHP.

The main goal of PHP is to enable users to easily develop dynamic Web pages. The difference between dynamic Web pages and static Web pages is that the content and structure of dynamic Web pages may change each time they are accessed (that's what the back-end programming is for) whereas the content and structure of static Web pages is fixed and does not change unless the designer manually changes them.

Unlike many other languages, PHP can be embedded directly into HTML, making it quite easy for those familiar with HTML to grasp how to add back-end, programmatic functionality to their Web pages. This single capability is one of the most important factors in PHP's usefulness, and thereby its popularity. But have no doubt that PHP is growing into a much more full-features language going well beyond the initial intentions of its authors. PHP intends to be the primary language for a great variety of online and offline applications, and PHP5 is showing every sign of doing just that.

And you shouldn't forget how well PHP works with HTTP (HyperText Transfer Protocol), the communications protocol (pre-agreed format for data communications) for Web. Whenever you click a link or enter a Web address into your browser, a request in HTTP format is sent to the Web server, which responds by sending back the Web page. If the Web page isn't found, you'll probably get the "404 Not Found" error. Sending back the correct page or sending an error if the page is not found are HTTP functions. We discuss HTTP thoroughly in Chapter 2 because several important aspects of PHP applications depend on HTTP.
Installing, Configuring, and Running PHP

Before you can write a PHP application that works with your Web pages, you need to have PHP installed and configured.

System Requirements
To run the code in this book you will need at least the following software:

Server software (an operating system such as Windows 2000 or Linux)

1. A PHP-compatible Web server (such as Apache or Internet Information Server (IIS)

2. PHP5 (get the download from www.php.net)

3. A relational database system (starting at Chapter 9, we use SQLite or MySQL)

4. A Web browser (such as IE, Mozilla, and so on)

5. A text editor, such as Notepad, Emacs, vi, BBEdit, and so on.
You shouldn't have to worry about hard drive space or RAM, unless you are working on a very old system, or one that is overloaded. PHP doesn't take up much room, and runs very efficiently.

You can run all of the software listed here on the same computer, for development purposes. If you have access to several networked computers, you may want to install all of your server software on one (typically either a UNIX or Windows NT/2000 computer), and use another networked computer as your client machine. For the purposes of this book, we will generally assume you are running all of the software on a single computer. This is the configuration used by most Web developers.

You can run all of the software listed here on the same computer, for development purposes. If you have access to several networked computers, you may want to install all of your server software on one (typically either a UNIX or Windows NT/2000 computer), and use another networked computer as your client machine. For the purposes of this book, we will generally assume you are running all of the software on a single computer. This is the configuration used by most Web developers.
php.ini, the PHP Configuration File
There are two examples of PHP configuration files that come with PHP when you download it: php.ini-dist and php.ini-recommended. After you download and install PHP, there will be one file named php.ini strategically placed on your system, and each time PHP starts it will read this file and set itself up accordingly. The php.ini file can be written out by hand, but of course most of us just modify either the dist or recommended file to suit our needs, and then copy and rename it into the appropriate folder.

However, you should note the following lines in the top of the dist file:

; This is the default settings file for new PHP installations.
; By default, PHP installs itself with a configuration suitable for
; development purposes, and *NOT* for production purposes.

The settings in the dist file are used for nearly all of the examples in this book and we'll let you know whenever the configuration settings are changed. But you will want to use the recommended file when you complete your applications and copy them over to your production server, and you should be aware that you may need to rewrite your code a little bit to work properly with the recommended file's configuration settings. We'll discuss this more as we go along.

Setting up a Test Machine
In this chapter, we'll walk through setting up PHP5 on a Red Hat Linux machine running the Apache Web server, as well as on a Windows 2000 machine running Internet Information Server (IIS). You can run PHP5 with many other operating systems and Web servers, so see the PHP5 documentation for installation and configuration on other servers. And there are a variety of installation methods you can use. For example, there is an automatic installer for the Windows version, whereas you can install the Linux version using RPMs (for some versions of Linux), and you can also download and compile the Linux versions from the original source code if you like. None of the installations are all that difficult if you follow procedures correctly, and the examples we provide are a good starting point for many of the installations available.

There are some third-party installers (often open-source and free) out there, if you want to look for them. For instance, you might try PHPTriad or Foxserv in Google.

Network Connections
If you don't already know, a computer doesn't need to be attached to the Internet, or even to a network, to run Web server software. If you install a Web server on a computer, it's always possible to access that Web server from a Web browser running on the same machine, even if it doesn't have a network card or modem. Of course, to download and install the software you need, you have to have access to an Internet connection. But you don't need it to be active just because you're running your Web server.

Once you have a Web server installed and running, you'll install PHP5 alongside it. There's some configuration required to tell the Web server how to run PHP programs, and we'll walk through that process before we start PHP. There is an automatic installer to be found with most distributions of PHP; we'll use a primarily manual process to illustrate what's happening during installation.

  Important 
What if it goes wrong? The README and INSTALL files that are included in most PHP downloads, as well as the PHP manual at www.php.net/manual/, provide detailed information which may be more up-to-date than the information here, which covers the PHP5.0.2 release.
Where do You Start?
There are two main installation paths from which to choose, and each simply depends on which operating system you're using:

Installing PHP5 with the Apache Web Server on Linux (we use Red Hat Fedora Linux)

Installing PHP5 with Microsoft Internet Information Server on Windows (we use Windows 2000)

PHP5 can be installed on a great variety of Web server/operating system combinations, including under Apache on Windows. The two systems we're using are the easiest to get working. If neither of them suits you, of course you can install whatever other configuration you want—you should still be able to run all of the examples in the book. Refer to the PHP5 manual for more general installation instructions.

Running PHP5

One of the basic choices to make when installing PHP5 with your Web server is whether to run it as a CGI binary or as a separate static or dynamic module. CGI (Common Gateway Interface) is a very useful way to run interpreters such as PHP5. Because of security risks (see the "Running as a CGI" section later in this chapter for more information), compiling PHP5 as a static or dynamic module is recommended under most circumstances. Our installations (on Linux and on Windows) load PHP as a separate SAPI (Server Application Programming Interface) module. On Windows, the ISAPI filter was used to run PHP as a SAPI module.

Although it is most common to run PHP in conjunction with a Web server, so that Web pages with a file extension such as .php are processed through the PHP interpreter before the finished page is sent back to the browser, there is also a command line utility that enables you to run PHP code from the command line. It is present from any of the installation types we demonstrate. You can find plenty of documentation about it on the PHP site (www.php.net).

Creating and running PHP Web applications in a satisfactory way implies that you are running (or have access to) a Web server upon which PHP is (or can be) installed, and that the installation has been tested and runs properly. It also implies that PHP has been (or can be) configured to support the needs of your PHP programs. There are a couple scenarios under which these requirements can be achieved:

1. You are running a desktop or server machine, operating system, and Web server compatible with PHP, and PHP has been installed and configured.

2. You are running a desktop or server machine connected to the Internet, with access to a Web hosting account supported by a Web server with which PHP has been installed and configured.

The vast majority of desktop machines run Windows 98, NT, 2000, 2003, and XP. In many cases you can get a free copy of Personal Web Server (PWS) and install it on a machine running one of these operating systems. PHP is compatible with PWS, so you can install and configure PHP on desktop machines running basic operating systems such as Windows 98. Server operating systems such as Windows NT, 2000, and 200, come with Internet Information Server (IIS). PHP is compatible with IIS, and you can install and configure PHP on these machines. Our Windows 2000 installation of PHP5 uses IIS as a Web server.

The majority of Web-hosting computers run some version of Linux, such as Debian, RedHat, FreeBSD, and so on. The Web server of choice for these machines is Apache. PHP is compatible with Linux and Apache, and you can install and configure PHP on these systems, but if you are not in charge of the Web-hosting computer (and many times you won't be) you'll probably have little control over the installation and configuration. If you find yourself in this position (for example, if you've been hired to work on an existing Web site running on someone else's server), you can simply verify the operating system, Web server software, and PHP version so you can cope with whatever you've have to work with as you develop your PHP programs.
Installing PHP5 with Linux and Apache

At the time of this writing, the very first release candidate of PHP5 was available, and that's the one we're using. But you may want to check the PHP site for more recent versions, and any notes about changes.

The combination of Linux, Apache, MySQL, and PHP is probably the most common production environment for running PHP Web servers. This combination of open-source software has been referred to by the acronym LAMP. If you run the same combination of software, you can benefit from the experiences of the many other people who've used this setup.

The PHP developers work very closely with the Apache and MySQL teams to ensure that advances in the three server systems are fully supported by the other components. However, at the time of this writing PHP5 is being distributed with SQLite rather than MySQL, because there is some concern about whether MySQL is still open source. This may not be a concern when you read this and begin developing, but it's worth noting.

Choosing Your Installation Method
As with other open-source software, you have the option of downloading the PHP and Apache source code (which, in both cases, is written in the C programming language) and compiling the programs yourself. If that sounds daunting (it's not actually as scary as it sounds), you can obtain precompiled versions in one of two forms: binary downloads, which are precompiled versions of the software that typically come with installation scripts to put all the required pieces into the necessary parts of your file system, and binary packages, which are available for systems that have a software package management system, such as the Red Hat Package Manager (RPM) for Linux, and are the easiest to install.

An RPM Installation of PHP4
The version of Red Hat we're using is actually called Fedora, because Red Hat has split off development into two parts: Fedora and the enterprise version of Red Hat Linux. Currently, the Fedora site doesn't have an RPM for PHP5, so we'll provide the instructions for getting and installing the RPM for PHP4 here, and then show how to download and compile PHP5 for Fedora later. By the time you read this, in all likelihood there will be an RPM available for PHP5 for your Linux distribution, so the RPM installation presented here should provide good guidance for installing PHP5 via the RPM method.

A number of popular Linux distributions use the Red Hat Package Manager, including Red Hat, SuSE, Mandrake, Definite, TurboLinux, Caldera, and Yellow Dog. If your system uses an alternative package management system, such as Debian's deb packages, refer to your distribution's manual for installation instructions.

Obtaining RPMs
The best place to get RPMs is almost always the disks from which you installed your Linux system. Red Hat 7 and SuSE 7 both include PHP4 (although it isn't installed by default)—by the time you read this, the same should be true of most current Linux distribution versions.
If your distribution doesn't include PHP4, or it doesn't include all the required functionality or support RPMs, then the next place to check is your Linux distribution vendor's Web site, which should have a download area or FTP site from which you can obtain the latest RPMs.

Finally, www.rpmfind.net provides a comprehensive search service for RPMs. When you download RPMs, though, make certain that they are compatible with your Linux distribution and your computer hardware. Different distributions put important files in different places, and this can lead to RPMs from different vendors not working on other systems. Most RPMs are available compiled to run on the different hardware systems that Linux supports.
Which RPM Packages do You Need?
1. zlib

2. libpng

3. libjpeg

4. gd

5. gd-devel

6. apache

7. mod_php4

You can find out which of them are already installed on your system by typing the following at a command prompt, substituting in the name of each of these packages in turn:

> rpm -q zlib
zlib-1.1.3-6-i386
> rpm -q libng
Package libpng is not installed
Note which of the packages you already have, and which versions they are (the version number is more important than the release number).

Apache is at version 1.3.29 if you want to remain at the old versions of GD, or 2.0.48 if you want to be current with the latest version of GD. Of course, if you are installing PHP5, GD is now bundled with PHP and is up to version 2.0.17

Then locate suitably up-to-date versions of all the packages that you don't have already, or have old versions for. As suggested, try your install CDs, your distributor's Web site, and www.rpmfind.net.

Once you have current versions of all the packages you need, you can install them. The command for upgrading an existing installation or installing a package for the first time is exactly the same. Navigate your command prompt to the location of the files on the CD or the directory into which you downloaded the RPMs. As root, type:

> rpm -Uh libpng-1.0.5-3-i386.rpm
##################

For each package you need to upgrade or install, just substitute the name of the package file you downloaded. The line of # signs extends across the screen as each installation progresses.

If you install the packages in the order listed previously, you should find that all the prerequisite files are installed in the necessary order.

To know more about PHP5 read next Post.I hope you will like it.