As you may have realized, the PHP language revolves around the central theme of practicality. PHP is about providing the programmer with the necessary tools to get the job done in a quick and efficient fashion. Five important characteristics make PHP’s practical nature possible:
• Familiarity
• Simplicity
• Efficiency
• Security
• Flexibility
One final characteristic makes PHP particularly interesting: it’s free!
Familiarity
Programmers from many backgrounds will find themselves already accustomed to the PHP language. Many of the language’s constructs are borrowed from C and Perl, and in many cases PHP code is almost indistinguishable from that found in the typical C or Pascal program. This minimizes the learning curve considerably.
Simplicity
A PHP script can consist of 10,000 lines or one line: whatever you need to get the job done. There is no need to include libraries, special compilation directives, or anything of the sort. The PHP engine simply begins executing the code after the first escape sequence (<?) and continues until it passes the closing escape sequence (?>). If the code is syntactically correct, it will be executed exactly as it is displayed.
Efficiency
Efficiency is an extremely important consideration for working in a multiuser environment such as the WWW. PHP 4.0 introduced resource allocation mechanisms and more pronounced support for object-oriented programming, in addition to session management features. Reference counting has also been introduced in the latest version, eliminating unnecessary memory allocation.
Security
PHP provides developers and administrators with a flexible and efficient set of security safeguards. These safeguards can be divided into two frames of reference: system level and application level.
System-Level Security Safeguards
PHP furnishes a number of security mechanisms that administrators can manipulate, providing for the maximum amount of freedom and security when PHP is properly configured. PHP can be run in what is known as safe mode, which can limit users’ attempts to exploit the PHP implementation in many important ways. Limits can also be placed on maximum execution time and memory usage, which if not controlled can have adverse affects on server performance. Much as with a cgi-bin folder, administrators can also place restrictions on the locations in which users can view and execute PHP scripts and use PHP scripts to view guarded server information, such as the passwd file.
Application-Level Security Safeguards
Several trusted data encryption options are supported in PHP’s predefined function set. PHP is also compatible with many third-party applications, allowing for easy-integration with secure ecommerce technologies. Another advantage is that the PHP source code is not viewable through the browser because the script is completely parsed before it is sent back to the requesting user. This benefit of PHP’s server-side architecture prevents the loss of creative scripts to users at least knowledgeable enough to execute a ‘View Source’.
Security is such an important issue that this book contains an entire chapter
on the subject. Please read Chapter 16, “Security,” for a thorough accounting of
PHP’s security features.
Flexibility
Because PHP is an embedded language, it is extremely flexible towards meeting the needs of the developer. Although PHP is generally touted as being used in conjunction solely with HTML, it can also be integrated alongside languages like JavaScript, WML, XML, and many others. Additionally, as with most other mainstream languages, wisely planned PHP applications can be easily expanded as needed. Browser dependency is not an issue because PHP scripts are compiled entirely on the server side before being sent to the user. In fact, PHP scripts can be sent to just about any kind of device containing a browser, including cell phones, personal digital assistant (PDA) devices, pagers, laptops, not to mention the traditional PC. People who want to develop shell-based applications can also execute PHP from the command line. Since PHP contains no server-specific code, users are not limited to a specific
and perhaps unfamiliar Web server. Apache, Microsoft IIs, Netscape Enterprise Server, Stronghold, and Zeus are all fair game for PHP’s server integration. Because of the various platforms that these servers operate on, PHP is largely platform independent, available for such platforms as UNIX, Solaris, FreeBSD, and Windows 95/98/NT. Finally, PHP offers access to external components, such as Enterprise Java Beans and Win32 COM objects. These newly added features put PHP in the big league, truly enabling developers to scale PHP projects upward and outward as need be.
Free
The open source development strategy has gained considerable notoriety in the software industry. The prospect of releasing source code to the masses has resulted in undeniably positive outcomes for many projects, perhaps most notably Linux, although the success of the Apache project has certainly been a major contributor in proving the validity of the open source ideal. The same holds true for the developmental history of PHP, as users worldwide have been a huge factor in the advancement of the PHP project. PHP’s embracing of this open source strategy result in great performance gains for users, and the code is available free of charge. Additionally, an extremely receptive user community numbering in the thousands acts as “customer support,” providing answers to even the most arcane questions in popular online discussion groups. The next section, “User Affirmations,” provides testimonies from three noted industry professionals. Each provides keen insight into why they find PHP such an appealing technology.
Sunday, October 26, 2008
An Introduction to PHP
The past five years have been fantastic in terms of the explosive growth of the Internet and the new ways in which people are able to communicate with one another. Spearheading this phenomenon has been the World Wide Web (WWW), with thousands of new sites being launched daily and consumers being consistently offered numerous outstanding services via this new communications medium. With this exploding market has come a great need for new technologies and developers to learn these technologies. Chances are that if you are reading this paragraph, you are one of these Web developers or are soon to become one. Regardless of your profession, you’ve picked this book up because you’ve heard of the great new technology called PHP. This chapter introduces the PHP language, discusses its history and capabilities, and provides the basic information you need to begin developing PHPenabled sites. Several examples are provided throughout, hopefully serving to excite you about what PHP can offer you and your organization. You will learn how to install and configure the PHP software on both Linux/UNIX and Windows machines, and you will learn how to embed PHP in HTML. At the conclusion of the chapter, you will be ready to begin delving into the many important aspects of the PHP language. So light the fire, turn on your favorite jazz album, and curl up on the lazyboy; you are about to learn what will be one of the most exciting additions to your resume: PHP programming.
PHP set its roots in 1995, when an independent software development contractor named Rasmus Lerdorf developed a Perl/CGI script that enabled him to know how many visitors were reading his online resume. His script performed two duties: logging visitor information and displaying the count of visitors to the Web page. Because the WWW as we know it today was still so young at that time, tools such as these were nonexistent, and they prompted emails inquiring about Lerdorf’s scripts. Lerdorf thus began giving away his toolset, dubbed Personal Home Page (PHP), or Hypertext Preprocessor. The clamor for the PHP toolset prompted Lerdorf to begin developing additions to PHP, one of which converted data entered in an HTML form into symbolic variables that allowed for their export to other systems. To accomplish this, he opted to continue development in C code rather than Perl. This addition to the 3 existing PHP toolset resulted in PHP 2.0, or PHP-FI (Personal Home Page—Form Interpreter). This 2.0 release was accompanied by a number of enhancements
and improvements from programmers worldwide. The new PHP release was extremely popular, and a core team of developers soon formed. They kept the original concept of incorporating code directly alongside HTML and rewrote the parsing engine, giving birth to PHP 3.0. By the 1997 release of version 3.0, over 50,000 users were using PHP to enhance their Web pages. Development continued at a hectic pace over the next two years, with hundreds of functions being added and the user count growing in leaps and bounds. At the onset of 1999, Netcraft reported a conservative estimate of a user base surpassing 1,000,000, making PHP one of the most popular scripting languages in the world. Early 1999 saw the announcement of the upcoming PHP 4.0. Although one of PHP’s strongest features was its proficiency at executing scripts, the developers had not intended that large-scale applications were going to be built using PHP. Thus they set out to build an even-more robust parsing engine, better known as Zend. Development continued rapidly, culminating in the May 22, 2000, release of PHP 4.0. In addition to the Zend processor, Zend technologies, based in Israel, offers the Zend optimizer, which increases even further the performance benefits of the Zend parsing engine. Available for download free of charge, the benchmarks have shown that the optimizer can result in a 40 to 100 percent overall performance gain. Check out the Zend site for more information. At the time of this writing, according to Netcraft, PHP is installed on over 3.6 million domains, making it one of the most popular scripting languages in the world. The future of PHP indeed looks bright, as major Web sites and personal users alike continue to embrace the product. PHP is best summarized as an embedded server-side Web-scripting language that provides developers with the capability to quickly and efficiently build dynamic Web applications. PHP bears a close resemblance, both syntactically and grammatically, to the C programming language, although developers haven’t been shy to integrate features from a multitude of languages, including Perl, Java, and C++. Several of these valuable borrowed features include regular expression parsing, powerful array-handling capabilities, an object-oriented methodology, and vast database support. For writing applications that extend beyond the traditional, static methodology of Web page development (that is, HTML), PHP can also serve as a valuable tool for creating and managing dynamic content, embedded directly beside the likes of JavaScript, Stylesheets, WML (Wireless Markup Language) and many other useful languages. Providing hundreds of predefined functions, PHP is capable of handling just about anything a developer can dream of. Extensive support is offered for graphic creation and manipulation, mathematical calculations, ecommerce, and burgeoning technologies such as Extensible Markup Language (XML), open database connectivity (ODBC), and Macromedia Shockwave. This vast range of capabilities eliminates the need for the tedious and costly integration of several third-party modules, making PHP the tool of choice for developers worldwide. One of the main strengths of PHP is the fact that because it can be embedded directly alongside HTML code, there is no need to write a program that has many commands just to output the HTML. HTML and PHP can be used interchangeably as needed, working alongside one another in unison. With PHP, we can simply do the following:
<html> <title><? print "Hello world!"; ?></title>
</html> And Hello world! will be displayed in the Web page title bar. Interestingly, the single line print statement is enclosed in what are commonly known as PHP’s escape characters () is a complete program. No need for lengthy prefacing code or inclusion of libraries; the only required code is what is needed to get the job done! Of course, in order to execute a PHP script, you must first install and configure the PHP software on your server. This process is explained in “Downloading and Installing PHP/Apache,” later in this chapter. Immediately preceding that section are a few excerpts from prominent users testifying to the power of PHP, followed by a detailed synopsis of the language and its history. However, before diving into the installation process, take a moment to read more about the characteristics of PHP that make it such a powerful language. This is the subject of the next section, aptly titled “Characteristics of PHP.”
An Abbreviated History
PHP set its roots in 1995, when an independent software development contractor named Rasmus Lerdorf developed a Perl/CGI script that enabled him to know how many visitors were reading his online resume. His script performed two duties: logging visitor information and displaying the count of visitors to the Web page. Because the WWW as we know it today was still so young at that time, tools such as these were nonexistent, and they prompted emails inquiring about Lerdorf’s scripts. Lerdorf thus began giving away his toolset, dubbed Personal Home Page (PHP), or Hypertext Preprocessor. The clamor for the PHP toolset prompted Lerdorf to begin developing additions to PHP, one of which converted data entered in an HTML form into symbolic variables that allowed for their export to other systems. To accomplish this, he opted to continue development in C code rather than Perl. This addition to the 3 existing PHP toolset resulted in PHP 2.0, or PHP-FI (Personal Home Page—Form Interpreter). This 2.0 release was accompanied by a number of enhancements
and improvements from programmers worldwide. The new PHP release was extremely popular, and a core team of developers soon formed. They kept the original concept of incorporating code directly alongside HTML and rewrote the parsing engine, giving birth to PHP 3.0. By the 1997 release of version 3.0, over 50,000 users were using PHP to enhance their Web pages. Development continued at a hectic pace over the next two years, with hundreds of functions being added and the user count growing in leaps and bounds. At the onset of 1999, Netcraft reported a conservative estimate of a user base surpassing 1,000,000, making PHP one of the most popular scripting languages in the world. Early 1999 saw the announcement of the upcoming PHP 4.0. Although one of PHP’s strongest features was its proficiency at executing scripts, the developers had not intended that large-scale applications were going to be built using PHP. Thus they set out to build an even-more robust parsing engine, better known as Zend. Development continued rapidly, culminating in the May 22, 2000, release of PHP 4.0. In addition to the Zend processor, Zend technologies, based in Israel, offers the Zend optimizer, which increases even further the performance benefits of the Zend parsing engine. Available for download free of charge, the benchmarks have shown that the optimizer can result in a 40 to 100 percent overall performance gain. Check out the Zend site for more information. At the time of this writing, according to Netcraft, PHP is installed on over 3.6 million domains, making it one of the most popular scripting languages in the world. The future of PHP indeed looks bright, as major Web sites and personal users alike continue to embrace the product. PHP is best summarized as an embedded server-side Web-scripting language that provides developers with the capability to quickly and efficiently build dynamic Web applications. PHP bears a close resemblance, both syntactically and grammatically, to the C programming language, although developers haven’t been shy to integrate features from a multitude of languages, including Perl, Java, and C++. Several of these valuable borrowed features include regular expression parsing, powerful array-handling capabilities, an object-oriented methodology, and vast database support. For writing applications that extend beyond the traditional, static methodology of Web page development (that is, HTML), PHP can also serve as a valuable tool for creating and managing dynamic content, embedded directly beside the likes of JavaScript, Stylesheets, WML (Wireless Markup Language) and many other useful languages. Providing hundreds of predefined functions, PHP is capable of handling just about anything a developer can dream of. Extensive support is offered for graphic creation and manipulation, mathematical calculations, ecommerce, and burgeoning technologies such as Extensible Markup Language (XML), open database connectivity (ODBC), and Macromedia Shockwave. This vast range of capabilities eliminates the need for the tedious and costly integration of several third-party modules, making PHP the tool of choice for developers worldwide. One of the main strengths of PHP is the fact that because it can be embedded directly alongside HTML code, there is no need to write a program that has many commands just to output the HTML. HTML and PHP can be used interchangeably as needed, working alongside one another in unison. With PHP, we can simply do the following:
<html> <title><? print "Hello world!"; ?></title>
</html> And Hello world! will be displayed in the Web page title bar. Interestingly, the single line print statement is enclosed in what are commonly known as PHP’s escape characters () is a complete program. No need for lengthy prefacing code or inclusion of libraries; the only required code is what is needed to get the job done! Of course, in order to execute a PHP script, you must first install and configure the PHP software on your server. This process is explained in “Downloading and Installing PHP/Apache,” later in this chapter. Immediately preceding that section are a few excerpts from prominent users testifying to the power of PHP, followed by a detailed synopsis of the language and its history. However, before diving into the installation process, take a moment to read more about the characteristics of PHP that make it such a powerful language. This is the subject of the next section, aptly titled “Characteristics of PHP.”
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