如何从表的下拉列表中将值传递给$ _GET

the situation I am facing is like that:

I read data from a database and dump them into a table in a webpage. And then, according to a column's value, show a drop-down list or not. And write the value from the drop-down list back into the database.

I use ...Submit, but the $_GET has no values about the drop-down list.

I list the whole code set here.

Any help is highly appreciated!

$GCdataSQL = "select * from table_name";
$GCdata = new Query($GCdataSQL);

$table = "<form method='GET'><table class='datatable table table-condensed ' id='query-data'><thead><tr>";
$ColName = array('col1','col2','col3','col4', 'col5', 'col6', 'col7', 'col8');
foreach ($ColName as $Name){
    $table .= "<th>$Name</th>";
}
$table .= "</tr></thead><tbody>";
while ($GCdataRow = $GCdata->fetchRow()){
        $emplid = $GCdataRow['emplid'];
        $term = $GCdataRow['term'];
        $handled = $GCdataRow['handled'];
    if ($GCdataRow['code'] == 'UNKNOW' || $GCdataRow['code'] == 'Not Repeated'){$GCdataRow['code']= '';}

    if ($GCdataRow['local_action'] !== $GCdataRow['new_action']){
        $table .=  "<tr bgcolor= 'LightPink'>"; 

    }
    else {
        $table .=  "<tr>";
    }

    foreach($GCdataRow as $key=>$value){

        if ($key == 'emplid'){
            $table .="<td><a href='link' target = '_blank'>$value</a></td>";
        }
        else if ($key == 'new_action'){
            $table .="<td><a href='link' target = '_blank'>$value</a></td>";
        }
        else if ($key == 'handled' && $handled == 'Not Reviewed'){

            $table .="<td><select name = 'handlecode'><option value = 'Not Reviewed'>Not Reviewed</option><option value = 'Handled by Script'>Handled by Script</option><option value = 'Handled Manually'>Handled Manually</option><option value = 'Leave It'>Leave It</option></select></td>";

        }
        else {
            $table .=  "<td>".htmlentities($value)."</td>"; 
            }

        }

        $table .=  "</tr>";
        $loopcount++;
    }

    if(isset($table)) {$table .=  "</tbody></table>";}
   echo $table;
   echo "<button type='submit' class = 'btn btn-primary' style = 'position: absolute; left:50%;' >Submit</button></form>";

finally I changed the form method to POST, and everything is fine! Now the values are in $_POST, and I could use them to insert into the database!

Thank you!