Professional Information Technology-Programming Book part 91 docx

Introducing PEAR PEAR is a framework and distribution system for reusable PHP packages. PEAR is made up of the following:  A structured library of open-source code for PHP developers  A system for distributing and maintaining code in packages  The PEAR Coding Standards (PCS)  The PHP Foundation Classes (PFC)  Online support for the PEAR community through a website and mailing list The PEAR Code Library PEAR brings together many different open-source projects, each of which is bundled into its own package. Each PEAR package has its own maintainers and developers, who determine the changes and release cycle for their own packages, but the package structure is consistent for all PEAR projects. You use the PEAR installer, which is shipped with PHP, to automatically download and install a PEAR package by simply giving its name. You will learn how to use the PEAR installer later in this lesson. Each package may have dependencies from other PEAR packages, and this is explicitly noted in the documentation, even if packages appear to be related because of their names. A package tree structure exists within PEAR, and an underscore character (_) separates nodes in the hierarchy. For instance, the HTTP package contains various HTTP utilities, whereas HTTP_Header deals specifically with HTTP header requests. Package Distribution and Maintenance PEAR packages are registered in a central database at http://pear.php.net. The PEAR website provides a searchable interface to the database by package name, category, and release date. Maintainers of PEAR packages use the PEAR website to manage their projects. A CVS server allows developers to collaborate on source code and, once a release has been agreed upon, it can be made available from this central location immediately. PEAR Coding Standards The PCS documents were created because many different teams are developing open-source packages that might be of use to the PHP community. The documents in PCS outline a structured way in which code should be written in order for a package to be accepted as part of the PEAR project. The standards are quite detailed and contain mostly points of style, such as identifier naming conventions and a consistent style to use when declaring functions and classes. This may sound a little daunting, but as your scripts become more complicated, you will realize how important it is to write readable code, and you will begin to develop a clear coding style. The PCS documentation simply formalizes a set of guidelines for writing readable PHP. You can find the PCS documents online at http://pear.php.net/manual/en/standards.php. PHP Foundation Classes PFC is a subset of PEAR packages, and these classes have a strict set of entrance criteria:  Quality Packages must be in a stable state.  Generality Packages should not be excessively specific to any particular type of environment.  Interoperability Packages should work well with other packages and in different environments, and they should have a standardized API.  Compatibility Packages must be designed to be backward compatible when new features are added. At the present time, only the PEAR installer is shipped with PHP. However, at a later date, certain classes may be included as standard. The PFC would be those classes. Online Support for PEAR The PEAR website, at http://pear.php.net, includes comprehensive online documentation for the PEAR project. The package database can be searched via the website, and package maintainers can log in to update their project details. There are a number of mailing lists for PEAR users, maintainers, core developers, and webmasters. You can join any or all of these lists by using the form at http://pear.php.net/support/lists.php. Using PEAR In the following sections you will learn how to use PEAR to find and install packages on a system, and you'll learn how to submit your own projects for consideration as PEAR packages. Finding a PEAR Package On every page of the PEAR website is a search box that you can use to search the package database. You simply enter a name, or part of a name, and all matching packages are displayed. Searching Packages To perform a detailed search on a package name, maintainer, or release date, you can use the form at http://pear.php.net/package-search.php. You can click the name of the package you are interested in from the search results. The page that is then displayed should give some key information about that package, including a summary of its features, the current release version, and status and infor mation about its dependenciesthat is, any other PEAR packages that are required for this package to work. The tabs at the top of the package details page allow you to view the documentation. If you are unsure from the summary information about exactly what you can achieve by using a particular package, you can browse through the documentation pages. If you simply want to browse all the available PEAR packages, you can go to the categorized list at http://pear.php.net/packages.php. Using the PEAR Installer When you have decided that a package will be useful, you can download it from the web by using the tab at the top of its package information page. However, using the PEAR installer program is a quick and easy way to manage packages within a PHP installation. The installer is able to find and download the latest version of a package and can also install it for you automatically. The PEAR installer is named pear. To run the installer, you run the pear command followed by a command option. To see all the packages currently installed on a system, you can use the list command option: $ pear list Command Options Running pear with no arguments brings up a list of all the available command options. The output produced should be similar to the following: Installed packages: =================== Package Version State DB 1.6.2 stable HTTP 1.2.2 stable Net_DNS 1.00b2 beta Net_SMTP 1.2.6 stable Net_Socket 1.0.1 stable PEAR 1.3.2 stable SQLite 1.0.2 stable Each package name, the version installed, and its release status are shown. The actual packages installed on your system may differ from the ones shown here. You can use the search command option to search the PEAR package database. To search for all packages that contain the string mail, you run the following command: # pear search mail The output produced displays all matching packages, their latest version numbers, and a brief summary. The search performed is not case-sensitive. To view all the available stable PEAR packages, you use the list-all command: # pear list-all This produces a long list! To download and install a package, you use the install command option followed by the name of the package. To install the Mail package, you issue the following command: # pear install Mail_Queue Some packages cannot be installed unless others are already installed on your system, and installation will fail if the required packages are not found. The following output shows an attempt to install the Mail_Queue package before the Mail package has been installed: # pear install Mail_Queue downloading Mail_Queue-1.1.3.tar Starting to download Mail_Queue-1.1.3.tar (-1 bytes) done: 98,816 bytes requires package `Mail' Mail_Queue: Dependencies failed Some dependencies are optional. When you install the Mail package to fix the dependency reported in the previous error message, PEAR advises you that the functionality of the Mail package can be enhanced if you also install Net_SMTP: # pear install Mail downloading Mail-1.1.4.tar Starting to download Mail-1.1.4.tar (-1 bytes) done: 73,728 bytes Optional dependencies: package `Net_SMTP' version >= 1.1.0 is recommended to utilize some features. install ok: Mail 1.1.4 You can use the upgrade command option to download and install a later version of an installed package. To check whether a new version of the Mail package is released, you use the following command: # pear upgrade Mail If a later version than the one installed is found, it is upgraded automatically. Upgrading Packages You can use the upgrade-all command to check for newer versions of all your installed PEAR packages at once. If you want to remove a PEAR package completely, you use the uninstall command. Contributing Your Own PEAR Project If you have written a PHP project that you think will be useful to other developers, you might consider submitting a proposal to have it included in PEAR. The online documentation (at http://pear.php.net/manual/en/guide-newmaint.php) includes a guide for project maintainers that details the process of first making su re that your project is suitable for submission to PEAR and then ensuring that your code is of a suitable standard. You should read that guide if you intend to write a package suitable for use by other developers. Even if your project is not suitable for PEAR, these guidelines will make you think about your software design and coding standards and will help you produce a much higher-quality package. Summary In this lesson you have learned how to use PEAR. Now that you have completed this book, you can take advantage of the many freely available PEAR classes so that you can create PHP scripts that perform a wide variety of functions. Happy coding! Appendix A. Installing PHP If you need to install PHP for yourself, this appendix is for you: It takes you through the process step-by-step, on both Linux/Unix and Windows platforms. . you to view the documentation. If you are unsure from the summary information about exactly what you can achieve by using a particular package, you can browse through the documentation pages Packages must be in a stable state.  Generality Packages should not be excessively specific to any particular type of environment.  Interoperability Packages should work well with other packages. website is a search box that you can use to search the package database. You simply enter a name, or part of a name, and all matching packages are displayed. Searching Packages To perform a detailed