php单例型(singleton pattern)

搞定，吃饭

<?php
/*
The purpose of singleton pattern is to restrict instantiation of class to a single object. It
is implemented by creating a method within the class that creates a new instance of
that class if one does not exist. If an object instance already exists, the method simply
returns a reference to an existing object.
*/

class Logger {
    private static $instance;

    public static function getInstance() {
        if (!isset(self::$instance)) {
            self::$instance = new self;
        }
        return self::$instance;
    }

    public function logNotice($msg) {
        return 'logNotice: ' . $msg . '<br/>';
    }

    public function logWaring($msg) {
        return 'logWaring: ' . $msg . '<br/>';
    }

    public function logError($msg) {
        return 'logError: ' . $msg . '<br/>';
    }
}

echo Logger::getInstance()->logNotice('test-log-notice');
echo Logger::getInstance()->logWaring('test-log-waring');
echo Logger::getInstance()->logError('test-log-error');
?>