编辑从php中的数据库动态加载的选择框值

Question

I have three select boxes which populate with data from the database.
First they are acquiring data from the DB fine, but when it comes to editing the second select box is taking the default value from the database.

Here is the code for the Main Category :

<select name="cat" id="cat">
<?php 
$res="SELECT * from cat order by catname";
$stmt = $conn->prepare( $res );
$stmt->execute();
while($result = $stmt->fetch(PDO::FETCH_ASSOC)) {
    echo "<option value=$cate>$result[catname]</option>";
}
?>
</select>

Sub Category:

<select name="scid" id="scid">
<?php
if ($row['psubcat']>0) {
    $resi="SELECT * from subcat where sid=$row[psubcat]";
    $stmt = $conn->prepare( $resi );
    $stmt->execute();
    while($results = $stmt->fetch(PDO::FETCH_ASSOC)) {
        echo "<option value=$row[psubcat]>$results[scname]</option>";
    }
}
?>
</select>

Sub Sub Category:

<select name="sscid" id="sscid">
<?php
if ($sscate>0) {
    $resis="SELECT * from ssubcat where sid=$sscate";
    $stmt = $conn->prepare( $resis );
    $stmt->execute();
    while($resultss = $stmt->fetch(PDO::FETCH_ASSOC)) {
        echo "<option value=$sscate>$resultss[sscname]</option>";
    }
}
?>
</select>
</div>

Categories change dynamically depending on key change using ajax.

Answer 1

You need to query record which are subcategories of main category but make selection of stored db value subcategory. Sub Category:

<select name="scid" id="scid">
    <?php
    if ($row['psubcat']>0)
    {
        $resi="SELECT * from subcat where cat_id=$row['cat_id']";
        $stmt = $conn->prepare( $resi );
        $stmt->execute();
        while($results = $stmt->fetch(PDO::FETCH_ASSOC))
        {
            echo '<option value="'.$results[psubcat].'" '.($row[psubcat] == $results[psubcat] ? 'selected' : '').'>'.$results[scname].'</option>';
        }
    }
    ?>
</select>