[wolfgang1983]

Found the issue I had it like

PHP Code:

 "slideshow_module['" . $slideshow_module['key'] . "'][banner_id]" 


PHP Code:

<?php 

$option = array();

foreach ($banners as $key => $banner) { 
    $option[$banner['banner_id']] = $banner['name'];
}

echo form_dropdown("slideshow_module['" . $slideshow_module['key'] . "'][banner_id]", $option, $slideshow_module['banner_id'], array('class' => 'form-control'));

?>

It should of been 

PHP Code:

"slideshow_module[" . $slideshow_module['key'] . "][banner_id]"