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   2  <h1 id="401">My First PRADO Application</h1>
   3  <p>
   4  In this section, we guide you through creating your first PRADO application, the famous "Hello World" application.
   5  </p>
   6  <p>
   7  "Hello World" perhaps is the simplest <i>interactive</i> PRADO application that you can create. It displays to end-users a page with a submit button whose caption is <tt>Click Me</tt>. After the user clicks on the button, its caption is changed to <tt>Hello World</tt>.
   8  </p>
   9  <p>
  10  There are many approaches that can achieve the above goal. One can submit the page to the server, examine the POST variable, and generate a new page with the button caption updated. Or one can simply use JavaScript to update the button caption upon its <tt>onclick</tt> client event.
  11  </p>
  12  <p>
  13  PRADO promotes component-based and event-driven Web programming. The button is represented by a <tt>TButton</tt> object. It encapsulates the button caption as the <tt>Text</tt> property and associates the user button click action with a server-side <tt>OnClick</tt> event. To respond to the user clicking on the button, one simply needs to attach a function to the button's <tt>OnClick</tt> event. Within the function, the button's <tt>Text</tt> property is modified as "Hello World". The following diagram shows the above sequence,
  14  </p>
  15  <img src="<%~sequence.gif%>" />
  16  <p>
  17  Our PRADO application consists of three files, <tt>index.php</tt>, <tt>Home.page</tt> and <tt>Home.php</tt>, which are organized as follows,
  18  </p>
  19  <img src="<%~directory.gif%>" />
  20  <p>
  21  where each directory is explained as follows. Note, the above directory structure can be customized. For example, one can move the <tt>protected</tt> directory out of Web directories. You will know how to do this after you go through this tutorial.
  22  </p>
  23  <ul>
  24  <li><tt>assets</tt> - directory storing published private files. See <a href="?page=Advanced.Assets">assets</a> section for more details. This directory must be writable by the Web server process.</li>
  25  <li><tt>protected</tt> - application base path storing application data and private script files. This directory should be configured as inaccessible to end-users.</li>
  26  <li><tt>runtime</tt> - application runtime storage path storing application runtime information, such as application state, cached data, etc. This directory must be writable by the Web server process.</li>
  27  <li><tt>pages</tt> - base path storing all PRADO pages.</li>
  28  </ul>
  29  
  30  <div class="tip">
  31  <b class="tip">Tip:</b>You may also use the <tt>framework/prado-cli.php</tt> 
  32  <a href="?page=GettingStarted.CommandLine">command line script</a> 
  33  to create the Prado project directory structure. For example, type the command
  34  <tt>php path/to/prado-cli.php -c helloworld</tt> in the directory
  35  where you want to create the <tt>helloworld</tt> project.
  36  </div>
  37  
  38  <p>
  39  The three files that we need are explained as follows.
  40  </p>
  41  <ul>
  42  <li><tt>index.php</tt> - entry script of the PRADO application. This file is required by all PRADO applications and is the only script file that is directly accessible by end-users. Content in <tt>index.php</tt> mainly consists of the following three lines,
  43  <com:TTextHighlighter CssClass="source">
  44  require_once('path/to/prado.php');  // include the prado script
  45  $application=new TApplication;      // create a PRADO application instance
  46  $application->run();                // run the application
  47  </com:TTextHighlighter>
  48  </li>
  49  <li><tt>Home.page</tt> - template for the default page returned when users do not explicitly specify the page requested. A template specifies the presentational layout of components. In this example, we use two components, <tt>TForm</tt> and <tt>TButton</tt>, which correspond to the &lt;form&gt; and &lt;input&gt; HTML tags, respectively. The template contains the following content,
  50  <com:TTextHighlighter Language="prado" CssClass="source">
  51  <html>
  52    <body>
  53      &lt;com:TForm&gt;
  54        &lt;com:TButton Text="Click me" OnClick="buttonClicked" /&gt;
  55      &lt;/com:TForm&gt;
  56    </body>
  57  </html>
  58  </com:TTextHighlighter>
  59  </li>
  60  <li><tt>Home.php</tt> - page class for the <tt>Home</tt> page. It mainly contains the method responding to the <tt>OnClick</tt> event of the button.
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  62  class Home extends TPage
  63  {
  64      public function buttonClicked($sender,$param)
  65      {
  66          // $sender refers to the button component
  67          $sender->Text="Hello World!";
  68      }
  69  }
  70  </com:TTextHighlighter>
  71  </li>
  72  </ul>
  73  <p>
  74  The application is now ready and can be accessed via: <tt>http://Web-server-address/helloworld/index.php</tt>, assuming <tt>helloworld</tt> is directly under the Web <tt>DocumentRoot</tt>. Try to change <tt>TButton</tt> in <tt>Home.page</tt> to <tt>TLinkButton</tt> and see what happens.
  75  </p>
  76  <p>
  77  Complete source code of this demo can be found in the PRADO release. You can also try the <a href="http://www.pradosoft.com/demos/helloworld/">online demo</a>.
  78  </p>
  79  
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