PHP MySQL - Stilson.net

www.it-ebooks.infoC H A P T E R 10• • •Working with the File andOperating SystemThese days it’s rare to write an application that is entirely self-sufficient—that is, one that does not relyon at least some level of interaction with external resources, such as the underlying file and operatingsystem or even other programming languages. The reason for this is simple: as languages, file systems,and operating systems mature, the opportunities for creating much more efficient, scalable, and timelyapplications increases greatly as a result of the developer’s ability to integrate the most powerful featuresof each technology into a singular product. Of course, the trick is to choose a language that offers aconvenient and efficient means for doing so. Fortunately, PHP satisfies both conditions quite nicely,offering the programmer a wonderful array of tools not only for handling file system input and output,but also for executing programs at the shell level. This chapter serves as an introduction to thesefeatures, including the following topics:• Files and directories: You’ll learn how to perform file system forensics, revealingdetails such as file and directory size and location, modification and access times,and more.• File I/O: You’ll learn how to interact with data files, which will let you perform avariety of practical tasks, including creating, deleting, reading, and writing files.• Directory contents: You’ll learn how to easily retrieve directory contents.• Shell commands: You can take advantage of operating system and otherlanguage-level functionality from within a PHP application through a number ofbuilt-in functions and mechanisms.• Sanitizing input: This section demonstrates PHP’s input sanitization capabilities,showing you how to prevent users from passing data that could potentially causeharm to your data and operating system.■ Note PHP is particularly adept at working with the underlying file system, so much so that it is gainingpopularity as a command-line interpreter, a capability introduced in version 4.2.0. This topic is beyond the scopeof this book, but you can find additional information in the PHP manual.229