$client = new SoapClient('mybaseurl/api/v2_soap?wsdl=1');
$session = $client->login('myuser','mypass');
$filter = array('filter' => array(array('key' => 'status', 'value' => 'processing')));
$results = $client->salesOrderList($session, $filter);

$fromDate = date('Y-m-d H:i:s', strtotime('-1 days'));
$todayDate = date('Y-m-d H:i:s');
$filter = array('filter' => array(array('key' => 'created_tat', 'value' => array('from'=>$fromDate, 'to'=>$todayDate))));