Object-Oriented Features New to PHP 5
PHP 3 was released in mid-1998. Some basic object-oriented (OO) capabilities were included, more or less as an afterthought, to "provide new ways of accessing arrays."1
No significant changes were made to the object model when version 4 was released in mid-2000. The basics of object-oriented programming (OOP) were there -- you could create a class and single inheritance was supported.
With the release of PHP 5 in 2004 there was plenty of room for improving PHP's OO capabilities. At this point, Java, the most popular OO language to date, had already been around for almost 10 years. Why did it take PHP so long to become a full-fledged OO language? The short answer is because PHP is principally a web development language and the pressures of web development have only recently pushed it in this direction.
Support for objects has been grafted onto the language -- you can choose to use objects or simply revert to procedural programming. That PHP is a hybrid language should be viewed as something positive, not as a disadvantage. There are some situations where you will simply want to insert a snippet of PHP and other situations where you will want to make use of its OO capabilities.
As I have already argued in Chapter 1, in some cases, an OO solution is the only solution. PHP 5 recognizes this fact and incorporates a full-blown object model, consolidating PHP's position as the top server-side scripting language.
Like Chapter 2, this will be a chapter of broad strokes. I'll give a general overview of how the object model has been improved, and then I'll get into the details using concrete examples in later chapters. I'll also address the issue of backward compatibility.
Chapter 2 identified access modifiers as an essential element of an OO language. PHP 5 gives us everything we would expect in this area. In previous versions of PHP there was no support for data protection, meaning that all elements of a class were publicly accessible. This lack of access modifiers was probably the biggest disincentive to using objects in PHP 4.
NOTE: A notion closely related to data protection is information hiding. Access modifiers make information hiding possible by exposing an interface (as defined in Chapter 2). This is also referred to as encapsulation of an object.
Every OOP language comes with some built-in classes, and PHP is no exception. PHP 5 introduces the Standard PHP Library (SPL), which provides a number of ready-made classes and interfaces. As of version 5.1, depending upon how PHP is configured, all in all, there are well over 100 built-in classes and interfaces -- a healthy increase from the number available in version 5.0.
Having ready-made objects speeds up development, and native classes written in C offer significant performance advantages. Even if these built-in classes don't do exactly what you want, they can easily be extended to suit your needs.
NOTE: There are far too many classes for us to deal with all of them in this book, and some are still not very well documented. We'll focus on the classes that are especially noteworthy.
All OOP languages support exceptions, which are the OO way of handling errors. In order to use exceptions, we need the keywords try, catch, and throw. A try block encloses code that may cause an error. If an error occurs, it is thrown and caught by a catch block. The advantage of exceptions over errors is that exceptions can be handled centrally, making for much cleaner code. Exceptions also significantly reduce the amount of error-trapping code you need to write, which offers welcome relief from an uninspiring task. Also, having a built-in exception class makes it very easy to create your own customized exceptions through inheritance. (You'll learn how to make the transition from error trapping to exception handling in the section "Replacing Errors with Exceptions" on page 79.)
Because PHP is all about building dynamic web pages, database support is all-important. PHP 5 introduces the mysqli (MySQL Improved) extension with support for the features of MySQL databases versions 4.1 and higher. You can now use features such as prepared statements with MySQL, and you can do so using the built-in OO interface. In fact, anything you can do procedurally can also be done with this interface.
SQLite is a database engine that is incorporated directly into PHP. It is not a general-purpose database like MySQL, but it is an ideal solution in some situations, in many cases producing faster, leaner, and more versatile applications. Again an entirely OO interface is provided.
PHP versions 5.1 and higher also bundle PHP Data Objects (PDO) with the main PHP distribution. If you need to communicate with several different database back ends, then this package is the ideal solution. PDO's common interface for different database systems is only made possible by the new object model.
Given the importance of databases, we'll deal with them extensively in this book. We'll develop a MySQL database class starting with Chapter 9. In Chapter 15 we'll look at SQLite, and in Chapter 16 we'll discuss PDO.
Practical Task Scheduling Deployment
July 20, 2016 12:00 pm CDT
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
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With all the industry talk about the benefits of Linux on Power and all the performance advantages offered by its open architecture, you may be considering a move in that direction. If you are thinking about analytics, big data and cloud computing, you would be right to evaluate Power. The idea of using commodity x86 hardware and replacing it every three years is an outdated cost model. It doesn’t consider the total cost of ownership, and it doesn’t consider the advantage of real processing power, high-availability and multithreading like a demon.
This ebook takes a look at some of the practical applications of the Linux on Power platform and ways you might bring all the performance power of this open architecture to bear for your organization. There are no smoke and mirrors here—just hard, cold, empirical evidence provided by independent sources. I also consider some innovative ways Linux on Power will be used in the future.Get the Guide