PHP Cookbook

20.7. Responding to User Actions

Problem

You want to do something when a user clicks a button, chooses an item from a dropdown list, or otherwise interacts with a GUI widget.

Solution

Write a callback function and then associate the callback function with a signal using the connect( ) method:

// create the window
$window = &new GtkWindow();

// create a button with the current time as its label
$button = &new GtkButton(strftime('%c'));

// set the update_time() function as the callback for the "clicked" signal
$button->connect('clicked','update_time');

function update_time($b) {
    // the button's text is in a child of the button - a label widget
    $b_label = $b->child;
    // set the label text to the current time
    $b_label->set_text(strftime('%c'));
}

// add the button to the window
$window->add($button);

// display the window
$window->show_all();

// necessary so that the program exits properly
function shutdown() { gtk::main_quit(); }
$window->connect('destroy','shutdown');

// start GTK's signal handling loop
gtk::main();

Discussion

The code in the Solution displays a window with a button in it. On the button is the time, rendered by strftime('%c') . When the button is clicked, its label is updated with the current time.

The update_time( ) function is called each time the button is clicked because $button->connect('clicked','update_time') makes update_time( ) the callback function associated with the button’s clicked signal. The first argument to the callback function is the widget whose ...