Explode for selected

Hi all,

I have trouble on this code,

In DB "planCurrencies" = "1,2,3,4"

PHP Code:

<select class="select2" name="currency[]" style="width: 100%" multiple="multiple" data-placeholder="Choose">
    <?php
    $cid = explode(',',$plan->planCurrencies);
    foreach($this->currencies_model->get() as $c) { ?>
    <option value="<?php echo $c->ID; ?>" <?php echo $c->ID == $cid ? "selected":"" ?>><?php echo $c->currencyCode; ?></option>
    <?php } ?>
</select> 


This code already show all currencies but selected currency not working,

Thanks you