select dropdown value according to previous valuesubmit new one - php

Question

I use the following code to select all value from a DB table and put it in dropdown. Here is the code :
<select name="dis_name">
<?php
$qu="Select DISTINCT name from root";
$res=mysqli_query($con,$qu);
while($r=mysqli_fetch_row($res))
{
echo "<option value='$r[0]'> $r[0] </option>";
}
?>
Based on previous code a value is selected and submitted. I want to show previously selected value in dropdown on another page so i use following code:
<select name="dis_name">
<option value="RAM"<?php echo $r20 == "RAM" ? " selected" : ""; ?>>RAM</option>
<option value="ROHAN"<?php echo $r20 == "ROHAN" ? " selected" : ""; ?>>ROHAN</option>
</select>
This code work fine till no new value added in DB table. But whenever i add new value i have to update edit code manually. Is there any way, so that dropdown previous selection updated automatically in edit page.

Answer 1

Add the condition in your loop, eg:
<?php
while($r=mysqli_fetch_row($res))
{
echo "<option value='$r[0]'";
if ($r[0] == $r20) echo " selected";
echo "> $r[0] </option>";
}
?>

Answer 2

If I get what you want (assuming that $r20 is the previously selected value:
<?php
$qu="Select DISTINCT name from root";
$res=mysqli_query($con,$qu);
while($r=mysqli_fetch_row($res))
{
echo "<option value='$r[0]'";
if($r[0]==$r20){echo 'selected="selected"';}
echo "> $r[0] </option>";
}
?>
this way the select will display as selected the option that match the $r20 value dinamically.
BTW, you should use id in your code. This way you could also have more than one user with the same name (but different ID). With DISTINCT, as you are doing, if you have more than one user with the same name you will get only one.