PHP从单一答案选项字段更改为隐藏字段

I have a working code where the result of a query is passed to another page. The query comes with only a single answer which is what I want. What I want however is for the field I am passing to be hidden. There is also an option field with multiple answers being passed at the same time, which has to remain. So what I'm asking is for a proper way to pas the hidden field so I don't get all the errors when I do it the way I was trying (ie The wrong way)

Here's the working code that I have. I want the first option field to be a hidden field. Any help is appreciated

    $studentquery="SELECT * from student ORDER BY ssurname";<br>

    //Do Query
    $studentresult = mysql_query ($studentquery);
      $options="";  
    echo "<form action='addstudenttofamily1c.php' method='POST'>";      


    $familychoice = "SELECT * from hostfamily WHERE hid= '".mysql_real_escape_string($hostfamily). "'";
    $resultfamilychoice = mysql_query ($familychoice);

    $options2="";
    echo "<select name='element_1' id='element_1'>";

    while ($rowfam=mysql_fetch_array($resultfamilychoice))
    {
        echo "<option value='$rowfam[hid]'>$rowfam[hfsurname] $rowfam[hfmname]</option><br/>";
    }
    echo "</select>";


    echo "<select name='element_3' id='element_3'>";

    while($row=mysql_fetch_array($studentresult))
    {
        echo "<option value='$row[sid]'>$row[sname] $row[ssurname]</option>";
    }

    echo "</select><input type='submit' name='submit3' value='Replace Student'>";
    echo "</form>";

    echo"</td>";
    echo"      </tr>";

This is how you can store a hidden value for a form:

<input type="hidden" name="SomeHiddenField" val="ValueOfThisField" />

To which you could code it in PHP to make it dynamic also.