# Universal Class Loader # Universal Class Loader [*Phalcon\\Loader*](#) is a component that allows you to load project classes automatically,based on some predefined rules. Since this component is written in C, it provides the lowest overhead inreading and interpreting external PHP files. The behavior of this component is based on the PHP's capability of [autoloading classes](http://www.php.net/manual/en/language.oop5.autoload.php). If a class that doesnot exist is used in any part of the code, a special handler will try to load it.[*Phalcon\\Loader*](#) serves as the special handler for this [operation.By](http://operation.By) loading classes on a need to load basis, the overall performance is increased since the only filereads that occur are for the files needed. This technique is called [lazy initialization](http://en.wikipedia.org/wiki/Lazy_initialization). With this component you can load files from other projects or vendors, this autoloader is [PSR-0](https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-0.md) and [PSR-4](https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-4.md) compliant. [*Phalcon\\Loader*](#) offers four options to autoload classes. You can use them one at a time or combine them. ### 注册命名空间（Registering Namespaces） If you're organizing your code using namespaces, or external libraries do so, the registerNamespaces() provides the autoloading mechanism. Ittakes an associative array, which keys are namespace prefixes and their values are directories where the classes are located in. The namespaceseparator will be replaced by the directory separator when the loader try to find the classes. Remember always to add a trailing slash atthe end of the paths. ``` <pre class="calibre14">``` <?php use Phalcon\Loader; // Creates the autoloader $loader = new Loader(); // Register some namespaces $loader->registerNamespaces( array( "Example\Base" => "vendor/example/base/", "Example\Adapter" => "vendor/example/adapter/", "Example" => "vendor/example/" ) ); // Register autoloader $loader->register(); // The required class will automatically include the // file vendor/example/adapter/Some.php $some = new Example\Adapter\Some(); ``` ``` ### 注册前缀（Registering Prefixes） This strategy is similar to the namespaces strategy. It takes an associative array, which keys are prefixes and their values are directorieswhere the classes are located in. The namespace separator and the “\_” underscore character will be replaced by the directory separator whenthe loader try to find the classes. Remember always to add a trailing slash at the end of the paths. ``` <pre class="calibre14">``` <?php use Phalcon\Loader; // Creates the autoloader $loader = new Loader(); // Register some prefixes $loader->registerPrefixes( array( "Example_Base" => "vendor/example/base/", "Example_Adapter" => "vendor/example/adapter/", "Example_" => "vendor/example/" ) ); // Register autoloader $loader->register(); // The required class will automatically include the // file vendor/example/adapter/Some.php $some = new Example_Adapter_Some(); ``` ``` ### 注册文件夹（Registering Directories） The third option is to register directories, in which classes could be found. This option is not recommended in terms of performance,since Phalcon will need to perform a significant number of file stats on each folder, looking for the file with the same name as the [class.It](http://class.It)'s important to register the directories in relevance order. Remember always add a trailing slash at the end of the paths. ``` <pre class="calibre14">``` <?php use Phalcon\Loader; // Creates the autoloader $loader = new Loader(); // Register some directories $loader->registerDirs( array( "library/MyComponent/", "library/OtherComponent/Other/", "vendor/example/adapters/", "vendor/example/" ) ); // Register autoloader $loader->register(); // The required class will automatically include the file from // the first directory where it has been located // i.e. library/OtherComponent/Other/Some.php $some = new Some(); ``` ``` ### 注册类名（Registering Classes） The last option is to register the class name and its path. This autoloader can be very useful when the folder convention of theproject does not allow for easy retrieval of the file using the path and the class name. This is the fastest method of autoloading.However the more your application grows, the more classes/files need to be added to this autoloader, which will effectively makemaintenance of the class list very cumbersome and it is not recommended. ``` <pre class="calibre14">``` <?php use Phalcon\Loader; // Creates the autoloader $loader = new Loader(); // Register some classes $loader->registerClasses( array( "Some" => "library/OtherComponent/Other/Some.php", "Example\Base" => "vendor/example/adapters/Example/BaseClass.php" ) ); // Register autoloader $loader->register(); // Requiring a class will automatically include the file it references // in the associative array // i.e. library/OtherComponent/Other/Some.php $some = new Some(); ``` ``` ### 额外的扩展名（Additional file extensions） Some autoloading strategies such as “prefixes”, “namespaces” or “directories” automatically append the “php” extension at the end of the checked file. If youare using additional extensions you could set it with the method “setExtensions”. Files are checked in the order as it were defined: ``` <pre class="calibre14">``` <?php // Creates the autoloader $loader = new \Phalcon\Loader(); // Set file extensions to check $loader->setExtensions(array("php", "inc", "phb")); ``` ``` ### 修改当前策略（Modifying current strategies） Additional auto-loading data can be added to existing values in the following way: ``` <pre class="calibre14">``` <?php // Adding more directories $loader->registerDirs( array( "../app/library/", "../app/plugins/" ), true ); ``` ``` Passing “true” as second parameter will merge the current values with new ones in any strategy. ### 安全层（Security Layer） Phalcon\\Loader offers a security layer sanitizing by default class names avoiding possible inclusion of unauthorized files.Consider the following example: ``` <pre class="calibre14">``` <?php // Basic autoloader spl_autoload_register(function ($className) { if (file_exists($className . '.php')) { require $className . '.php'; } }); ``` ``` The above auto-loader lacks of any security check, if by mistake in a function that launch the auto-loader,a malicious prepared string is used as parameter this would allow to execute any file accessible by the application: ``` <pre class="calibre14">``` <?php // This variable is not filtered and comes from an insecure source $className = '../processes/important-process'; // Check if the class exists triggering the auto-loader if (class_exists($className)) { // ... } ``` ``` If ‘../processes/important-process.php' is a valid file, an external user could execute the file withoutauthorization. To avoid these or most sophisticated attacks, Phalcon\\Loader removes any invalid character from the class namereducing the possibility of being attacked. ### 自动加载事件（Autoloading Events） In the following example, the EventsManager is working with the class loader, allowing us to obtain debugging information regarding the flow of operation: ``` <pre class="calibre14">``` <?php $eventsManager = new \Phalcon\Events\Manager(); $loader = new \Phalcon\Loader(); $loader->registerNamespaces( array( 'Example\\Base' => 'vendor/example/base/', 'Example\\Adapter' => 'vendor/example/adapter/', 'Example' => 'vendor/example/' ) ); // Listen all the loader events $eventsManager->attach('loader', function ($event, $loader) { if ($event->getType() == 'beforeCheckPath') { echo $loader->getCheckedPath(); } }); $loader->setEventsManager($eventsManager); $loader->register(); ``` ``` Some events when returning boolean false could stop the active operation. The following events are supported: Event NameTriggeredCan stop operation?beforeCheckClassTriggered before starting the autoloading processYespathFoundTriggered when the loader locate a classNoafterCheckClassTriggered after finish the autoloading process. If this event is launched the autoloader didn't find the class fileNo### 注意事项（Troubleshooting） Some things to keep in mind when using the universal autoloader: - Auto-loading process is case-sensitive, the class will be loaded as it is written in the code - Strategies based on namespaces/prefixes are faster than the directories strategy - If a cache bytecode like [APC](http://php.net/manual/en/book.apc.php) is installed this will used to retrieve the requested file (an implicit caching of the file is performed) | - [索引](# "总目录") - [下一页](# "日志记录（Logging）") | - [上一页](# "多语言支持（Multi-lingual Support）") |