WordPress TinyMCE customizing

functions.php

<?php
// Custom font format button
add_filter( 'mce_buttons', 'my_mce_buttons' );
function my_mce_buttons( $buttons ) {
		array_unshift( $buttons, 'styleselect' ); // Add custom format selector
		$remove = 'formatselect'; if ( ( $key = array_search( $remove, $buttons ) ) !== false ) unset( $buttons[$key] ); // Remove default format selector
    return $buttons;
}

// Custom font styles
add_filter( 'tiny_mce_before_init', 'custom_style_formats' );
function custom_style_formats( $init_array ) {
    $style_formats = array(
	array(
	    'title' => '.h1',
	    'block' => 'span',
	    'classes' => 'overskrift1',
	    'wrapper' => true,
	),
	array(
	    'title' => '.h2',
	    'block' => 'span',
	    'classes' => 'overskrift2',
	    'wrapper' => true,
	),
	array(
	    'title' => '.h3',
	    'block' => 'span',
	    'classes' => 'overskrift3',
	    'wrapper' => true,
	),
	array(
	    'title' => '.h4',
	    'block' => 'span',
	    'classes' => 'overskrift4',
	    'wrapper' => true,
	),
	array(
	    'title' => '.h5',
	    'block' => 'span',
	    'classes' => 'overskrift5',
	    'wrapper' => true,
	),
    );
    $init_array['style_formats'] = json_encode( $style_formats );
    return $init_array;
}

// Custom editor-style in TinyMCE
add_filter( 'mce_css', 'fb_mcekit_editor_style');
function fb_mcekit_editor_style($url) {
    $url = get_stylesheet_directory_uri() . '/editor-style.css';
    return $url;
}
?>