WordPress: Custom TinyMCE styles dropdown

<?php
add_editor_style();

add_filter( 'mce_buttons_2', 'wpmidia_mce_buttons_2' );

function wpmidia_mce_buttons_2( $buttons ) {
    array_unshift( $buttons, 'styleselect' );
    return $buttons;
}

add_filter( 'tiny_mce_before_init', 'wpmidia_mce_before_init' );

function wpmidia_mce_before_init( $settings ) {

    $style_formats = array(
        array(
            'title' => 'Button',
            'selector' => 'a',
            'classes' => 'button'
        ),
        array(
            'title' => 'Callout Box',
            'block' => 'div',
            'classes' => 'callout',
            'wrapper' => true
        ),
        array(
            'title' => 'Bold Red Text',
            'inline' => 'span',
            'styles' => array(
                'color' => '#f00',
                'fontWeight' => 'bold'
            )
        )
    );

    $settings['style_formats'] = json_encode( $style_formats );

    return $settings;

}

/* Style Format Options

title [required]              label for this dropdown item

selector|block|inline         selector limits the style to a specific HTML
[required]                    tag, and will apply the style to an existing tag
                              instead of creating one

                              block creates a new block-level element with the
                              style applied, and will replace the existing block
                              element around the cursor

                              inline creates a new inline element with the style
                              applied, and will wrap whatever is selected in the
                              editor, not replacing any tags

classes [optional]            space-separated list of classes to apply to the
                              element

styles [optional]             array of inline styles to apply to the element
                              (two-word attributes, like font-weight, are written
                              in Javascript-friendly camel case: fontWeight)

attributes [optional]         assigns attributes to the element (same syntax as styles)

wrapper [optional,            if set to true, creates a new block-level element
default = false]              around any selected block-level elements

exact [optional,              disables the “merge similar styles” feature, needed
default = false]              for some CSS inheritance issues

*/

?>