您还没有关闭 if 条件也没有关闭表格单元格

mysql不推荐使用mysqli或pdo

<select name="dato"><?
while ($datorow = mysql_fetch_array($dato)) {
    if ($datorow['Servicenum'] == $row['ID1']) {
        ?>
        <option value="something">something</option>
        <?
    }// here was the mistake
}
?></select>