Given the following which creates a set of checkboxes:

$db =& P4A_DB::singleton();
$clientlist = array();
$items = $db->fetchAll("SELECT * FROM microsites WHERE status=1 ORDER BY sitetitle");
foreach ($items as $item) {
$ci = $item['user'];
$cd = $item['sitetitle'];
$clientlist[] = array('id' => $ci, 'desc' => $cd);
}

$client_array_source =& $this->build("p4a_array_source", "client_array_source");
$client_array_source->load($clientlist)
->setPk("id");


$selectallbutton = $this->build("p4a_button","selectallbutton")
->setLabel('Select All');
$this->intercept($selectallbutton, 'onClick', 'selectall');

$this->build("p4a_field","clients")
->setWidth(300)
->setType("multicheckbox")
->setSource($client_array_source)
->setSourceDescriptionField("desc")
->setSourceValueField("id");


This function will allow the user to click the "select all" button and have their checkboxes populated:

function selectall() {
$array_id = array();
$num_rows = $this->clients->data->getNumRows();
for ($i = 1; $i $#60;= $num_rows; $i++) {
$this->clients->data->row($i);
$array_id[$i] = $this->clients->data->getPkValues();
}
$this->clients->setNewValue($array_id);
$this->clients->load();
}

This works in P4A v3.4.1 but not 3.4.0. I've not tested on later versions.