PHP 5 in Practice

8. Files and Directories As is necessary for any language, PHP has a complete set of file and directory support functions. However, one feature that makes these functions particularly useful in a web environment is the capability to operate ...

8.1. Generating a Full Directory Listing Most web servers display a list of all files in a directory for you, allowing users to select any one of their choosing. However, this is usually turned off for security reasons. You don't want users stum...

8.2. Natural Display of File Sizes Listing 8.1.1 gave a way to visibly display a directory listing. There was one odd part to it though. When displaying the file sizes, they were shown in bytes because this is what the size of a file is returned t...

8.3. Renaming All Files Within a Directory PHP is well known as a web programming language; however, it is also useful as a command-line scripting language. Most distributions of PHP now come with the command-line version by default. As an examp...

8.4. Search for Filenames Within a Directory Tree Another common task using the file system is the need to find a file of a certain name. This can be useful either in command-line programming to replace similar tools that the operating system prov...

8.5. Handling Relative and Absolute File Paths When working on the Web, or just with your local file system, you have to deal with the difference between a relative and an absolute file path. An absolute path contains the directory structure withi...

8.6. Reading a File Via HTTP or FTP Built into the core of the PHP file-handling system is support for accessing files across a network. All that you need to do to use this is use a full URL instead of a filename when using any file access funct...

8.7. Watching the Contents of a File As It Grows (Simulating UNIX tail -f) UNIX has a program called tail that is useful for watching the contents of a file. Normally it simply shows the last lines of a file; however, when invoked as tail -f it ke...

8.8. Generating a Difference Report Between Two Files Finding changes between two versions of a file is a common taskthat's why the UNIX program diff and other such utilities exist. It can be useful to have a PHP version of this utility, one that ...

8.9. Locking a File for Exclusive Use The Web, by its nature, will have multiple people running the same script/web page at the exact same time. This can cause a problem if you have a page that is updating a file. Two scripts can have race condi...

8.10. Caching Remote Files Locally Often a website may include files from another website. These could be graphics, XML data, JavaScript or even some embedded HTML. There are often good reasons for doing this, such as including a banner graphic ...

8.11. Compressing and Uncompressing Files File space and network bandwidth are always at a premium, and therefore compressing data is usually a good thing. PHP provides a set of functions that allow you to deal with compressed files and make them ...

8.12. Automatically Including Certain Files from the Parent Tree A semicommon templating technique is to have identically named files with variables and functions in them that vary for each subdirectory that they are in. This way you can customi...