Here is the code snippet :
<select name="isbn" onchange=" ">
<?php
//Displaying all ISBN in drop down
$result = mysqli_query($con,"SELECT * FROM book");
while($row = mysqli_fetch_array($result)) {
?>
<option> <?php echo $row['ISBN']; ?></option>
<?php } ?>
</select>
</label></td>
</tr>
<tr>
<td>Copy Number </td>
<td><select name="copy_number">
<?php
//Now based on selected book I want to fetch number of copies from database
$result = mysqli_query($con,"SELECT number_of_copies FROM book where isbn = [ SELECTE VALUE FROM ABOVE]");
?>
How can I do that?