[Plugin: Advanced Custom Fields] Multiple checkbox values not selected

$field[‘value’] for core/fields/checkbox.php in function create_field isn’t an array itself, but a CSV. As such, the in_array() call to set selected will never work. The fix is to convert the CSV to an array like below.

function create_field($field)
    {
        // defaults
        if(empty($field['value'])) {
            $field['value'] = array();
        } else {
            $field['value'] = explode(',', $field['value']);
        }
    ...
    }

Also, the correct way to check a checkbox is $selected = 'checked="checked"'; not $selected = 'checked="yes"';.

Great extension, especially now that I have the ability to pull in configurations via PHP code dynamically based upon my arbitrary conditions.

http://wordpress.org/extend/plugins/advanced-custom-fields/