96 lines
3.8 KiB
Markdown
96 lines
3.8 KiB
Markdown
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# Loading Classes
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Kohana takes advantage of PHP [autoloading](http://php.net/manual/language.oop5.autoload.php). This removes the need to call [include](http://php.net/include) or [require](http://php.net/require) before using a class. For instance, when you want to use the [Cookie::set] method, you just call:
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Cookie::set('mycookie', 'any string value');
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Or to load an [Encrypt] instance, just call [Encrypt::instance]:
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$encrypt = Encrypt::instance();
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Classes are loaded via the [Kohana::auto_load] method, which makes a simple conversion from class name to file name:
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1. Classes are placed in the `classes/` directory of the [filesystem](about.filesystem)
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2. Any underscore characters are converted to slashes
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2. The filename is lowercase
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When calling a class that has not been loaded (eg: `Session_Cookie`), Kohana will search the filesystem using [Kohana::find_file] for a file named `classes/session/cookie.php`.
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## Custom Autoloaders
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The default autoloader is enabled in `application/bootstrap.php` using [spl_autoload_register](http://php.net/spl_autoload_register):
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spl_autoload_register(array('Kohana', 'auto_load'));
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This allows [Kohana::auto_load] to attempt to load any class that does not yet exist when the class is first used.
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# Transparent Class Extension {#class-extension}
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The [cascading filesystem](about.filesystem) allows transparent class extension. For instance, the class [Cookie] is defined in `SYSPATH/classes/cookie.php` as:
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class Cookie extends Kohana_Cookie {}
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The default Kohana classes, and many extensions, use this definition so that almost all classes can be extended. You extend any class transparently, by defining your own class in `APPPATH/classes/cookie.php` to add your own methods.
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[!!] You should **never** modify any of the files that are distributed with Kohana. Always make modifications to classes using extensions to prevent upgrade issues.
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For instance, if you wanted to create method that sets encrypted cookies using the [Encrypt] class:
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<?php defined('SYSPATH') or die('No direct script access.');
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class Cookie extends Kohana_Cookie {
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/**
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* @var mixed default encryption instance
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*/
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public static $encryption = 'default';
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/**
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* Sets an encrypted cookie.
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*
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* @uses Cookie::set
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* @uses Encrypt::encode
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*/
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public static function encrypt($name, $value, $expiration = NULL)
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{
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$value = Encrypt::instance(Cookie::$encrpytion)->encode((string) $value);
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parent::set($name, $value, $expiration);
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}
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/**
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* Gets an encrypted cookie.
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*
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* @uses Cookie::get
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* @uses Encrypt::decode
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*/
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public static function decrypt($name, $default = NULL)
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{
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if ($value = parent::get($name, NULL))
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{
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$value = Encrypt::instance(Cookie::$encryption)->decode($value);
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}
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return isset($value) ? $value : $default;
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}
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} // End Cookie
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Now calling `Cookie::encrypt('secret', $data)` will create an encrypted cookie which we can decrypt with `$data = Cookie::decrypt('secret')`.
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## Multiple Levels of Extension {#multiple-extensions}
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If you are extending a Kohana class in a module, you should maintain transparent extensions. Instead of making the [Cookie] extension extend Kohana, you can create `MODPATH/mymod/encrypted/cookie.php`:
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class Encrypted_Cookie extends Kohana_Cookie {
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// Use the same encrypt() and decrypt() methods as above
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}
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And create `MODPATH/mymod/cookie.php`:
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class Cookie extends Encrypted_Cookie {}
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This will still allow users to add their own extension to [Cookie] with your extensions intact. However, the next extension of [Cookie] will have to extend `Encrypted_Cookie` instead of `Kohana_Cookie`.
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