Wordpress - custom wysiwyg buttons

custom-wysiwyg-buttons.php

<?php

add_filter('tiny_mce_before_init', 'customize_wysiwyg_buttons');

public function customize_wysiwyg_buttons($init) {
    $init['toolbar1'] = 'formatselect,styleselect,|,bold,italic,underline,|,bullist,numlist,|,link,unlink,|,removeformat';
    $init['toolbar2'] = '';
    $init['block_formats'] = 'Paragraph =p;Header 2 =h2;Header 3 =h3';

    return $init;
}