$tgl1 = date('Y-m-d', CDateTimeParser::parse($tgl1, 'dd-MM-yyyy'));  
$tgl2 = date('Y-m-d', CDateTimeParser::parse($tgl2, 'dd-MM-yyyy'));  

$data = Siswa::model()->findByAttributes(array('nisn' => $nisn)); 
$nama = $data->nama;