Generate dropdown lists which will send the selectted item back to server - php

Question

This code allows somebody to pick a class from a drop down menu, in which I convert numbers to alphabet letters. Now I want to send the selected value back to the server:
<table id="example" class="display table" style="width: 100%; cellspacing: 0;">
<thead>
<tr>
<th>Code</th>
<th>Name</th>
<th>Hours</th>
<th>Class</th>
<th>Add</th>
</tr>
</thead>
<tfoot>
<tr>
<th>Code</th>
<th>Name</th>
<th>Hours</th>
<th>Class</th>
<th>Add</th>
</tr>
</tfoot>
<tbody>
<?php
$query = "SELECT * FROM class";
$result = mysqli_query($connection,$query) or die ("Couldn’t execute query.");
while($row = mysqli_fetch_assoc($result))
{
echo "<tr>
<td>$row[code]</td>
<td>$row[name]</td>
<td>$row[hours]</td>";
$query1 = "SELECT total FROM classtot where code='$row[code]'";
$result1 = mysqli_query($connection,$query1);
while ($row=mysqli_fetch_assoc($result1))
{
$a=$row['total'];
}
$alphabet = range('A','Z');
$i = 1;
echo "
<td><select id='selectError' data-rel='chosen' name='class'>";
while ($i<=$a)
{
$kls=$alphabet[$i-1];
echo "<option value=$kls> $kls </option>";
$i=$i+1;
}
echo "</select></td>
<td>
<a class='btn btn-primary btn-addon m-b-sm btn-xs' href='home_member.php?page=add&id=$row[code]'>
<i class='fa fa-plus'></i> Add</a>
</td>
</tr>";
}
?>
</tbody>
</table>
How can I pass the slected value from the drop down menu 'class' to the server? I can pass the code, but don't know how to pass the selected class.

Answer 1

To add the chosen class to the URL, you will need to build the URL in JavaScript, because PHP does not know beforehand what the user will choose. Here is your code (only the part that goes through the SQL. In comments I describe several improvements I made (unrelated to your question):
<?php
// Make your query return ALL you need. Avoid second query:
$query = "SELECT class.code, class.name, class.hours, classtot.total
FROM class
INNER JOIN classtot ON classtot.code = class.code";
$result = mysqli_query($connection,$query) or die ("Couldn’t execute query.");
// Keep track of row number, for use in generating unique id property values
$rowIndex = 0;
while($row = mysqli_fetch_assoc($result))
{
$rowIndex++;
echo "<tr>
<td>$row[code]</td>
<td>$row[name]</td>
<td>$row[hours]</td>";
// Just pick the total from the combined query:
$a = $row['total'];
$alphabet = range('A','Z');
// Change id for select: You cannot assign the same id to several elements
echo "
<td><select id='select$rowIndex' data-rel='chosen' name='class' >";
// Use a zero-based for loop instead of a while
for ($i = 0; $i < $a; $i++)
{
// Reference $i now, not $i-1:
$kls = $alphabet[$i];
echo "<option value='$kls'> $kls </option>";
}
// Instead of hard-coding the URL, call a JS function that will make the url
echo "</select></td>
<td>
<a class='btn btn-primary btn-addon m-b-sm btn-xs' href='#'
onclick='gotoClass($rowIndex, \"$row[code]\")'>
<i class='fa fa-plus'></i> Add</a>
</td>
</tr>";
}
?>
</tbody>
</table>
<script>
// The JS function that builds the URL and triggers the navigation to it
function gotoClass(rowIndex, classCode) {
var sel = document.getElementById('select' + rowIndex);
location.href = 'home_member.php?page=add&id=' + classCode
+ '&something=' + sel.value;
return false;
}
</script>
In the above code, you need to change "something" to the correct URL parameter you want to use to pass the selected "alphabet" value.
If you have another select in the table rows, like this:
<select id='select2$rowIndex' data-rel='chosen' name='code' >
then extend the above javascript function as follows:
function gotoClass(rowIndex, classCode) {
var sel = document.getElementById('select' + rowIndex);
var sel2 = document.getElementById('select2' + rowIndex);
location.href = 'home_member.php?page=add&id=' + classCode
+ '&something=' + sel.value
+ '&othervalue=' + sel2.value;
return false;
}