Add class to link after form is submitted - php

Question

Im trying to add a class after a form is submitted depending on the option the user chose.
<form enctype="multipart/form-data" action="upload.php" method="POST">
title:<br />
<input type="text" name="title" value="" /> <br />
description:<br />
<input type="text" name="description" value="" /> <br />
Categories:<br />
<input type="checkbox" name="categories[]" value="1">Landscpae<br />
<input type="checkbox" name="categories[]" value="2">Portrait<br />
<input type="checkbox" name="categories[]" value="3">Monochrome<br />
Please choose an image: <input name="uploaded" type="file" /><br />
<input type="submit" value="Upload" />
</form>
<li class='INSERT OPTION HERE'> test </li>
With the option to select more than one class so add a space after each one.
on my database the Value="1" "2" "3" == the option name
let me know if more information is needed

Answer 1

Something along these lines might work:
$valid = array(1,2,3);#valid items
if(isset($_POST['categories']) && is_array($_POST['categories'])){
$post = array_unique($_POST['categories']);#you might not need this, but this removes duplicate values
foreach($post as $key => $value){
if(in_array($value, $valid)){
$class = true;
}else{
unset($post[$key]);#remove bad values, also this may not be necessary but removes unwanted items.
}
}
if(isset($class)){
$class = 'class="class' . implode(' class', $post) . '"';
}
}#else needed for non array categories?
<li <?php if(isset($class)){ echo $class;} ?> > test</li>
DEMO

Answer 2

You want to make sure that the form is submitted, and if it is then you echo a class and can create a switch statement that will alter the class depending on what was selected.
<li
<?php
if(isset($_POST['categories'])) {
echo 'class="';
switch($_POST['categories']) {
case 1;
echo 'class1';
break;
case 2;
echo 'class2';
break;
case 3;
echo 'class3';
break;
echo '"';
}
}
?>
> test </li>