如何在PHP中按下提交按钮后保持下拉选择的值？

Question

enter image description here I am using a dropdown list to show values in data tables. it's working but after press search button the dropdwon list clears.

<select name="staff" required>
    <option value="">Select Staff</option>
    <?php
        $query_subject = mysql_query("SELECT * from staffdet");

            while($row_subject = mysql_fetch_array($query_subject)) {
            ?>
    <option value="<?php echo $row_subject['staff_code'];?>"><?php echo $row_subject['staff_code']."-".$row_subject['staff_name'];?></option>
    <?php } ?>
</select>

How to keep selected dropdown list values?

Answer 1

IF you are submitting a form on same page with POST method then below code will solve your problem

<select name="staff" required>
<option value="">Select Staff</option>
<?php
    $query_subject = mysql_query("SELECT * from staffdet");

        while($row_subject = mysql_fetch_array($query_subject)) {
        ?>
        <option value="<?php echo $row_subject['staff_code'];?>" <?php if(!empty($_POST['staff']) && $_POST['staff']==$row_subject['staff_code']){echo 'selected="selected"';}?>>
            <?php echo $row_subject['staff_code']."-".$row_subject['staff_name'];?>
         </option>
<?php } ?>