How to get the selected value from dropdown on post edit - php

Question

I have the database for categories where i have id and name rows
<select name="category_id">
<option value="<?php if($category_id === 1) { echo 'selected';} ?>">Electronics</option>
<option value="<?php if($category_id === 2) { echo 'selected';} ?>">Automotive</option>
</select>
for some reason this does not show which one was selected when trying to edit the submitted post
and i do retrieve the category_id like so:
$res6 = mysql_query("SELECT * FROM `posts` WHERE `id` = '" . $id . "' LIMIT 1");
if(mysql_num_rows($res6) > 0){
while($row6 = mysql_fetch_assoc($res6)){
$id = $row6['id'];
$category_id = $row6['category_id'];
$price = $row6['price'];
$cover = $row6['cover'];
$title = $row6['title'];
$description = $row6['description'];
}
}

Answer 1

I think the option argument for selected is
<option selected="selected"> </option>

Answer 2

I believe MySQL results are always returned as strings, so $category_id === 1 will be false.
Either try $category_id === "1" or $category_id == 1
Also, you need to echo the selected="selected outside the value attribute

Answer 3

You can also try like this as well.
<select name="category_id">
<?php
$cats = array("1"=>"Electronics", "2"=>"Automotive");
foreach($cats as $k=>$cat){
if( $k == $category_id )
echo "<option value='{$k}' selected='selected'>{$cat}</options>";
else
echo "<option value='{$k}' >{$cat}</options>";
}
?>
</select>