Phalcon\Loader is an autoloader that implements PSR-4. Just like any autoloader, depending on its setup, it will try and find the files your code is looking for based on file, class, namespace etc. Since this component is written in C, it offers the lowest overhead when processing its setup, thus offering a performance boost.
This component relies on PHP’s autoloading classes capability. If a class defined in the code has not been included yet, a special handler will try to load it. Phalcon\Loader serves as the special handler for this operation. By loading classes on a need to load basis, the overall performance is increased since the only file reads that occur are for the files needed. This technique is called lazy initialization.
The component offers options for loading files based on their class, file name, directories on your file system as well as file extensions.
Usually we would use the spl_autoload_register() to register a custom autoloader for our application. Phalcon\Loader hides this complexity. After you define all your namespaces, classes, directories and files you will need to call the register() function, and the autoloader is ready to be used.
register() uses spl_autoload_register() internally. As a result it accepts also accepts the boolean prepend parameter. If supplied and is true, the autoloader will be prepended on the autoload queue instead of appended (default behavior).
You can always call the isRegistered() method to check if your autoloader is registered or not.
NOTE: If there is an error in registering the autoloader, the component will throw an exception.
Phalcon\Loader incorporates a security layer, by sanitizing class names by default i.e. removing invalid characters. As such it makes it more difficult for malicious code to be injected in your application.
The above auto loader lacks any kind of security. If a part of your code accidentally calls the auto loader with a name that points to a script containing malicious code, then your application will be compromised.
In the above snippet, if ../processes/important-process.php is a valid file, that could have been uploaded by a hacker or from a not so careful upload process, then an external user could execute the code without any authorization and subsequently get access to the whole application if not the server.
To avoid most of these kind of attacks, Phalcon\Loader removes invalid characters from the class name.
A very popular way to organize your application is with directories, each representing a particular namespace. Phalcon\Loader can register those namespace to directory mapping and traverse those directories to search the file that your application is requiring.
The registerNamespaces() method accepts an array, where keys are the namespaces and values are the actual directories in the file system. The namespace separator will be replaced by the directory separator when the loader tries to find the classes.
In the above example, whenever we reference a controller, the loader will search for it in app/controllers and its subdirectories. Similarly for a model the search will occur in app/models.
You do not need to register the sub namespaces, if the actual files are located in sub directories that map the namespace naming convention.
So for instance the above example defines our MyApp namespace to point to app/library. If we have a file:
that has a namespace of:
then the loader, as defined above, does not need to know about the MyApp\Components namespace location, or have it defined in the registerNamespaces() declaration.
If the component referenced in the code is MyApp\Components\Mail, it will assume that it is a sub directory of the root namespace. However, since we specified a different location for the MyApp\Controllers and MyApp\Models namespaces, the loader will look for those namespaces in the specified directories.
The registerNamespaces() method also accepts a second parameter merge. By default it is false. You can however set it to true when having multiple calls to registerNamespaces() so that the namespace definitions are merged.
The above example merges the second declaration of registerNamespaces() with the previous one.
If you need to check what namespaces are registered in the autoloader, you can use the getNamespaces() getter, which returns the array of the registered namespaces. For the example above, getNamespaces() returns:
Another way to let Phalcon\Loader know where your components/classes are located, so that the autoloader can load them properly, is by using registerClasses().
The method accepts an array, where the key is the namespaced class and the value is the location of the file that contains the class. As expected, this is the fastest way to autoload a class, since the autoloader does not need to do file scans or stats to find the files references.
However, using this method can hinder the maintenance of your application. The more your application grows, the more files are added, the easier it becomes to make a mistake while maintaining the list of files used in registerClasses()
In the above example, we are defining the relationship between a namespaced class and a file. As you can see, the loader will be as fast as it can be but the list will start growing, the more our application grows, making maintenance difficult. If however your application does not have that many components, there is no reason why you cannot use this method of autoloading components.
The registerClasses() method also accepts a second parameter merge. By default it is false. You can however set it to true when having multiple calls to registerClasses() so that the class definitions are merged.
There are times that you might need to require a specific file that contains a class without a namespace or a file that contains some code that you need. An example would be a file that contains handy debugging functions.
Phalcon\Loader offers registerFiles() which is used to require such files. It accepts an array, containing the file name and location of each file.
These files are automatically loaded when the register() method is called.
The registerFiles() method also accepts a second parameter merge. By default it is false. You can however set it to true when having multiple calls to registerFiles() so that the file definitions are merged.
You also have access to the loadFiles() method, which will traverse all the files registered and if they exist it will require them. This method is automatically called when you call register().
Another way to let Phalcon\Loader know where your application files are is to register directories. When a file needs to be required by the application, the autoloader will scan the registered directories to find the referenced file so that it can require it.
The registerDirs() method accepts an array with each element being a directory in the file system containing the files that will be required by the application.
This type of registration is not recommended in terms of performance. Additionally the order of declared directories matters, since the autoloader tries to locate the files by searching directories sequentially. As a result, the directory that contains the most referenced files should be declared first, etc.
The registerDirs() method also accepts a second parameter merge. By default it is false. You can however set it to true when having multiple calls to registerDirs() so that the class definitions are merged.
The above example merges the second declaration of registerDirs() with the previous one.
If you need to check what directories are registered in the autoloader, you can use the getDirs() getter, which returns the array of the registered directories. For the example above, getDirs() returns:
When you use the registerNamespaces() and registerDirs(), Phalcon\Loader automatically assumes that your files will have the .php extension. You can change this behavior by using the setExtensions() method. The method accepts an array, where each element is the extension to be checked (without the .):
In the example above, when referencing a file Mail, the autoloader will search in app/functions for the following files:
Files are checked in the order that each extension is defined.
File Checking Callback
You can speed up the loader by setting a different file checking callback method using the setFileCheckingCallback() method.
The default behavior uses is_file. However you can also use null which will not check whether a file exists or not, before loading it or you can use stream_resolve_include_path which is much faster than is_file but will cause problems if the target file is removed from the file system.
The [Events Manager][events] component offers hooks that can be implemented to observe or expand the functionality of the loader. The Phalcon\Loader implements the Phalcon\Events\EventsAwareInterface, and therefore the getEventsManager() and setEventsManager() methods are available.
The following events are available:
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Fires at the end of the auto load process when the class has not been found.
Fires at the beginning of the auto load process, before checking for the class.
Fires before checking a directory for a class file.
Fires when the loader locates a class file or a file in a registered directory
In the following example, the EventsManager is working with the class loader, offering additional information on the operation flow:
In the above example, we create a new Events Manager object, attach a method to the loader:beforeCheckPath event and then set it in our autoloader. Every time the loader loops and looks for a particular file in a specific path, the path will be printed on screen.
The getCheckedPath() holds the path that is scanned during each iteration of the internal loop. Also you can use the getfoundPath() method, which holds the path of the found file during the internal loop.
For events that can stop operation, all you will need to do is return false in the method that is attached to the particular event: