Need to change from dropdown to cheklist

Hello

I have this code implemented in my site, where users can self post. When somebody posting, he must to select category from dropdown menu:

<select name=”drop_cat” id=”drop_cat”>
<option value=””><?php echo attribute_escape(__(‘Izaberi kategoriju’)); ?></option>
<?php
$categories= get_categories();
foreach ($categories as $cat) {
$option = ‘<option value=”‘.$cat->category_nicename.'”>’;
$option .= $cat->cat_name;
$option .= ‘</option>’;
echo $option;
}

Now, can somebody help me to make similar code, but just to have ca checkbox / checklist where users can select multiple categories?

Pleeease heeeelp mee :))))