Settiing error delimiters in config/form_validation.php

You could try this:

PHP Code:

$config = array(
    
    'error_prefix' => '<div class="has-error">',
    'error_suffix' => '</div>',

    'membership_form' => array(
        array(
            'field' => 'member_name',
            'label' => 'Ad',
            'rules' => 'trim|required'
            ),
        // ...
        )
    );