+Sample: Hello World
+
+"Hello World" is the simplest interactive PRADO application that you can build. It displays to end-users a page with a submit button whose caption is Click Me. When the user clicks on the button, the button changes the caption to Hello World.
+
+
+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 onclick event.
+
+
+PRADO promotes component-based and event-driven Web programming. The button is represented by a TButton object. It encapsulates the button caption as the Text property and associates the user button click action with a server-side Click event. Therefore, the "Hello World" task can be handled intuitively and easily. One simply needs to attach a function to the button's Click event. Within the function, the button's Text property is modified as "Hello World". The following diagram shows the above sequence,
+
+
+
+The code that a developer needs to write is merely the following event handler function, where $sender refers to the button object.
+
+
+public function buttonClicked($sender,$param)
+{
+ $sender->Text="Hello World";
+}
+
+
+