Zend Framework教程-Loader以及PluginLoader

以下是具体用法，以及具体实现：

1.加载文件

使用方法：

Zend_Loader::loadFile($filename, $dirs=null, $once=false);

    /**     * Loads a PHP file.  This is a wrapper for PHP's include() function.     *     * $filename must be the complete filename, including any     * extension such as ".php".  Note that a security check is performed that     * does not permit extended characters in the filename.  This method is     * intended for loading Zend Framework files.     *     * If $dirs is a string or an array, it will search the directories     * in the order supplied, and attempt to load the first matching file.     *     * If the file was not found in the $dirs, or if no $dirs were specified,     * it will attempt to load it from PHP's include_path.     *     * If $once is TRUE, it will use include_once() instead of include().     *     * @param  string        $filename     * @param  string|array  $dirs - OPTIONAL either a path or array of paths     *                       to search.     * @param  boolean       $once     * @return boolean     * @throws Zend_Exception     */    public static function loadFile($filename, $dirs = null, $once = false)    {        self::_securityCheck($filename);        /**         * Search in provided directories, as well as include_path         */        $incPath = false;        if (!empty($dirs) && (is_array($dirs) || is_string($dirs))) {            if (is_array($dirs)) {                $dirs = implode(PATH_SEPARATOR, $dirs);            }            $incPath = get_include_path();            set_include_path($dirs . PATH_SEPARATOR . $incPath);        }        /**         * Try finding for the plain filename in the include_path.         */        if ($once) {            include_once $filename;        } else {            include $filename;        }        /**         * If searching in directories, reset include_path         */        if ($incPath) {            set_include_path($incPath);        }        return true;    }

  正如实现方法，有如下参数

$filename参数指定需要加载的文件，注意$filename不需要指定任何路径，只需要文件名即可。ZF会对文件作安全性检查。$filename 只能由字母，数字，连接符-,下划线_及英文句号.组成(半角)。$dirs参数则不限，可以使用中文等。

$dirs 参数用来指定文件所在目录，可以是一个字符串或者数组。如果为 NULL，则程序将会到系统的 include_path 下寻找文件是否存在（include_path可在php.ini中设置--Haohappy注），如果是字符串或数组，则会到指定的目录下去找，然后才是 include_path。

$once 参数为布尔类型，如果为 TRUE，Zend_Loader::loadFile() 使用 PHP 函数 ? include_once() 加载文件，否则就是 PHP 函数 ? include()。（本参数只能是true或false，两者区别就和include()和include_once()的区别一样。）

2.加载类

具体使用：

Zend_Loader::loadClass('Container_Tree',    array(        '/home/production/mylib',        '/home/production/myapp'    ));

具体实现：

/**     * Loads a class from a PHP file.  The filename must be formatted     * as "$class.php".     *     * If $dirs is a string or an array, it will search the directories     * in the order supplied, and attempt to load the first matching file.     *     * If $dirs is null, it will split the class name at underscores to     * generate a path hierarchy (e.g., "Zend_Example_Class" will map     * to "Zend/Example/Class.php").     *     * If the file was not found in the $dirs, or if no $dirs were specified,     * it will attempt to load it from PHP's include_path.     *     * @param string $class      - The full class name of a Zend component.     * @param string|array $dirs - OPTIONAL Either a path or an array of paths     *                             to search.     * @return void     * @throws Zend_Exception     */    public static function loadClass($class, $dirs = null)    {        if (class_exists($class, false) || interface_exists($class, false)) {            return;        }        if ((null !== $dirs) && !is_string($dirs) && !is_array($dirs)) {            require_once 'Zend/Exception.php';            throw new Zend_Exception('Directory argument must be a string or an array');        }        // Autodiscover the path from the class name        // Implementation is PHP namespace-aware, and based on        // Framework Interop Group reference implementation:        // http://groups.google.com/group/php-standards/web/psr-0-final-proposal        $className = ltrim($class, '');        $file      = '';        $namespace = '';        if ($lastNsPos = strripos($className, '')) {            $namespace = substr($className, 0, $lastNsPos);            $className = substr($className, $lastNsPos + 1);            $file      = str_replace('', DIRECTORY_SEPARATOR, $namespace) . DIRECTORY_SEPARATOR;        }        $file .= str_replace('_', DIRECTORY_SEPARATOR, $className) . '.php';        if (!empty($dirs)) {            // use the autodiscovered path            $dirPath = dirname($file);            if (is_string($dirs)) {                $dirs = explode(PATH_SEPARATOR, $dirs);            }            foreach ($dirs as $key => $dir) {                if ($dir == '.') {                    $dirs[$key] = $dirPath;                } else {                    $dir = rtrim($dir, '/');                    $dirs[$key] = $dir . DIRECTORY_SEPARATOR . $dirPath;                }            }            $file = basename($file);            self::loadFile($file, $dirs, true);        } else {            self::loadFile($file, null, true);        }        if (!class_exists($class, false) && !interface_exists($class, false)) {            require_once 'Zend/Exception.php';            throw new Zend_Exception("File "$file" does not exist or class "$class" was not found in the file");        }    }

$class 类名将会根据下划线（作为目录分隔线）对应到相应目录下的PHP文件，并加上'.php'，比如Container_Tree会指向ContainerTree.php。

$dir     可以是数组或者字符串。目录是除去类名包含的目录的路径。

 3.判断某个文件是否可读

具体使用：

if (Zend_Loader::isReadable($filename)) {    // do something with $filename}

具体实现：

    /**     * Returns TRUE if the $filename is readable, or FALSE otherwise.     * This function uses the PHP include_path, where PHP's is_readable()     * does not.     *     * Note from ZF-2900:     * If you use custom error handler, please check whether return value     *  from error_reporting() is zero or not.     * At mark of fopen() can not suppress warning if the handler is used.     *     * @param string   $filename     * @return boolean     */    public static function isReadable($filename)    {        if (is_readable($filename)) {            // Return early if the filename is readable without needing the            // include_path            return true;        }        if (strtoupper(substr(PHP_OS, 0, 3)) == 'WIN'            && preg_match('/^[a-z]:/i', $filename)        ) {            // If on windows, and path provided is clearly an absolute path,            // return false immediately            return false;        }        foreach (self::explodeIncludePath() as $path) {            if ($path == '.') {                if (is_readable($filename)) {                    return true;                }                continue;            }            $file = $path . '/' . $filename;            if (is_readable($file)) {                return true;            }        }        return false;    }

$filename参数指定了要检查的文件名，包括路径信息。这个方法是将 PHP 函数? is_readable()封装而成的，is_readable() 不会自动查找 include_path 下的文件，而 Zend::isReadable() 可以。

4.Autoloader

这个类的Autoloader功能已经不推荐使用了，所以不再讲述。还有其他的Autoloader，以后具体说明。

5.插件加载器

帮助文章给出的具体实例如下，可参考使用：

//////////////////////////////////

很多 Zend Framework 组件支持插件，允许通过指定类的前缀和到类的文件（不需要在 include_path或不需要遵循传统命名约定的文件）的路径动态加载函数。Zend_Loader_PluginLoader 提供了普通的函数来完成这个工作。

PluginLoader 的基本用法遵循 Zend Framework 的命名约定（一个文件一个类），解析路径时，使用下划线作为路径分隔符。当决定是否加载特别的插件类，允许传递可选的类前缀来预处理。另外，路径按 LIFO 顺序来搜索。由于 LIFO 搜索和类的前缀，允许命名空间给插件，这样可以从早期注册的路径来覆盖插件。

application/    modules/        foo/            views/                helpers/                    FormLabel.php                    FormSubmit.php        bar/            views/                helpers/                    FormSubmit.phplibrary/    Zend/        View/            Helper/                FormLabel.php                FormSubmit.php                FormText.php

<?php$loader = new Zend_Loader_PluginLoader();$loader->addPrefixPath('Zend_View_Helper', 'Zend/View/Helper/')       ->addPrefixPath('Foo_View_Helper', 'application/modules/foo/views/helpers')       ->addPrefixPath('Bar_View_Helper', 'application/modules/bar/views/helpers');?>

<?php// load 'FormText' helper:$formTextClass = $loader->load('FormText'); // 'Zend_View_Helper_FormText';// load 'FormLabel' helper:$formLabelClass = $loader->load('FormLabel'); // 'Foo_View_Helper_FormLabel'// load 'FormSubmit' helper:$formSubmitClass = $loader->load('FormSubmit'); // 'Bar_View_Helper_FormSubmit'?>

<?php// Store plugins in static registry 'foobar':$loader = new Zend_Loader_PluginLoader(array(), 'foobar');?>

<?phpif ($loader->isLoaded('Adapter')) {    $class   = $loader->getClassName('Adapter');    $adapter = call_user_func(array($class, 'getInstance'));}?>

具体插件加载器的实现可以参考Zend_Loader_PluginLoader和Zend_Loader。这里不在累述。

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