Show the selected value everytime in the dropdown list - html

Question

I need to display the selected category value displayed all the time. I have a list of category values and adding it to drop-down list from an array.
<form action="#" method="post">
<select name="dropDown" id="drop_down_id">
<option value=""> Select CATEGORY</option>
<?php
foreach($decoded as $key => $value ){
foreach($value as $key1 => $value1 ){
?> <option value="<?php echo $value1;?>"><?php echo $value1;?></option><?php
}
}
?>
<input type="submit" name="submit" value="Submit"/>
</form>

Answer 1

I see that you use post for form so you can use POST to know last selected:
$dropDown=htmlentities($_POST['dropDown'], ENT_QUOTES, "UTF-8");
And then just simple make if statement and its done:
if($dropDown==$value1){$selected='selected';}else{$selected=null;}
result:
<?php
$dropDown=htmlentities($_POST['dropDown'], ENT_QUOTES, "UTF-8");
?>
<form action="#" method="post">
<select name="dropDown" id="drop_down_id">
<option value=""> Select CATEGORY</option>
<?php
foreach($decoded as $key => $value ){
foreach($value as $key1 => $value1 ){
if($dropDown==$value1){$selected='selected';}else{$selected=null;}
echo '<option value="'.$value1.'" '.$selected.'>'.$value1.'</option>';
}
}
?>
<input type="submit" name="submit" value="Submit"/>
</form>
You can also store it in PHP SESSSION http://php.net/manual/en/function.session-start.php