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<h1>Applications</h1>
<p>
An application is an instance of <tt>TApplication</tt> or its derived class. It manages modules that provide different functionalities and are loaded when needed. It provides services to end-users. It is the central place to store various parameters used in an application. In a PRADO application, the application instance is the only object that is globally accessible via <tt>Prado::getApplication()</tt> function call.
</p>
<p>
Applications are configured via <a href="?page=Configurations.AppConfig">application configurations</a>. They are usually created in entry scripts like the following,
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require_once('/path/to/prado.php');
$application = new TApplication;
$application->run();
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where the method <tt>run()</tt> starts the application to handle user requests.
</p>

<h2>Directory Organization</h2>
<p>
A minimal PRADO application contains two files: an entry file and a page template file. They must be organized as follows,
</p>
<img src="<%~directory.gif%>" />
<ul>
<li><tt>wwwroot</tt> - Web document root or sub-directory.</li>
<li><tt>index.php</tt> - entry script of the PRADO application.</li>
<li><tt>assets</tt> - directory storing published private files. See <a href="?page=Advanced.Assets">assets</a> section.</li>
<li><tt>protected</tt> - application base path storing application data and private script files. This directory should be configured inaccessible to Web-inaccessible, or it may be located outside of Web directories.</li>
<li><tt>runtime</tt> - application runtime storage path. This directory is used by PRADO to store application runtime information, such as application state, cached data, etc.</li>
<li><tt>pages</tt> - base path storing all PRADO pages. See <a href="?page=Fundamentals.Services">services</a> section.</li>
<li><tt>Home.page</tt> - default page returned when users do not explicitly specify the page requested. This is a page template file. The file name without suffix is the page name. The page class is <tt>TPage</tt>. If there is also a class file <tt>Home.php</tt>, the page class becomes <tt>Home</tt>.</li>
</ul>

<p>
A product PRADO application usually needs more files. It may include an application configuration file named <tt>application.xml</tt> under the application base path <tt>protected</tt>. The pages may be organized in directories, some of which may contain page configuration files named <tt>config.xml</tt>. Fore more details, please see <a href="?page=Configurations.Overview">configurations</a> section.
</p>

<h2>Application Deployment</h2>
<p>
Deploying a PRADO application mainly involves copying directories. For example, to deploy the above minimal application to another server, follow the following steps,
</p>
<ol>
<li>Copy the content under <tt>wwwroot</tt> to a Web-accessible directory on the new server.</li>
<li>Modify the entry script file <tt>index.php</tt> so that it includes correctly the <tt>prado.php</tt> file.</li>
<li>Remove all content under <tt>assets</tt> and <tt>runtime</tt> directories and make sure both directories are writable by the Web server process.</li>
</ol>

<h2>Application Lifecycles</h2>
<p>
Like page lifecycles, an application also has lifecycles. Application modules can register for the lifecycle events. When the application reaches a particular lifecycle and raises the corresponding event, the registered module methods are invoked automatically. Modules included in the PRADO release, such as <tt>TAuthManager</tt>, are using this way to accomplish their goals.
</p>
<p>
The application lifecycles can be depicted as follows,
</p>
<img src="<%~applifecycles.gif%>" />

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