Selected rows not displaying when i display rows in Decrement order - php

Question

Background :
when a user selects one of the option [ example : Undelivered ] in the drop down menu, then i am displaying only the rows which have that value [ example : Undelivered ]
<tr><th>
<select id="my_select" onchange="send_option();">
<option value="all">Status</option>
<?php
$query = "SELECT DISTINCT in_transit FROM do_order";
$result = mysqli_query ($mysqli, $query);
while ( $row = mysqli_fetch_array($result) )
echo "<option value='" . $row['in_transit'] . "'>" . $row['in_transit'] . "</option>";
?>
</select>
</th></tr>
<?php
$theBigQuery = "SELECT * FROM do_order WHERE 1";
if (isset($_POST['my_option']) && $_POST['my_option'] != "")
{
if($_POST['my_option'] == "all")
{
}
else
{
$theBigQuery .= " AND in_transit like '" . $_POST["my_option"] . "'";
}
echo "<script type='text/javascript'>function changeOption(){document.getElementById('my_select').value='".$_POST['my_option']."';} changeOption();</script>";
}
$orderrecords = $db_handle->runSelectQuery($theBigQuery);
?>
<tr><td id="<?php echo $orderrecords[$k]["tracking_id"];?>">
<?php echo $orderrecords[$k]["in_transit"]; ?>
</td></tr>
<form method="post" action"dashboard.php" style="display:none" id="my_form">
<input type="text" id="my_option" name="my_option"/>
</form>
script
function send_option ()
{
var sel = document.getElementById( "my_select" );
var txt = document.getElementById( "my_option" );
txt.value = sel.options[ sel.selectedIndex ].value;
var frm = document.getElementById( "my_form" );
frm.submit();
}
Requirement :
Now I want to display rows in decrement order , so in above code i changed below line . now rows are displaying in decrement order.
$theBigQuery = "SELECT * FROM do_order ORDER BY id DESC";
Issue :
but if i select any option in dropdown [ example : undelivered ] , its not displaying any rows.

Answer 1

Using you edit, when you select an option, your query will become :
$theBigQuery = "SELECT * FROM do_order ORDER BY id DESC AND in_transit like 'Undelivered'";
This is a wrong sql query!!
So to fix this; leave the $theBigQuery as it was, and after the if (isset( .. test, before running the query, add the ORDER BY clause :
$theBigQuery = "SELECT * FROM do_order WHERE 1";
if (isset($_POST['my_option']) && $_POST['my_option'] != "")
{
if($_POST['my_option'] == "all")
{
}
else
{
$theBigQuery .= " AND in_transit like '" . $_POST["my_option"] . "'";
}
echo "<script type='text/javascript'>function changeOption(){document.getElementById('my_select').value='".$_POST['my_option']."';} changeOption();</script>";
}
$theBigQuery .= " ORDER BY id DESC";
$orderrecords = $db_handle->runSelectQuery($theBigQuery);