Wordpress Editor Styles

editor-styles.php

<?php
function custom_tinymce_styles( $settings ) {

	$style_formats_original = json_decode( $settings['style_formats'] );
	$style_formats          = array(

		// Inline style
		array(
			'title'   => 'Color Red',
			'inline'  => 'span',
			'classes' => 'red',
		),
		
		// Selector style
		array(
			'title'    => 'Button Info',
			'selector' => 'a',
			'classes'  => 'btn btn-info',
		),
		
		// Block style
		array(
			'title'   => 'Big',
			'block'   => 'p',
			'classes' => 'big',
		),

	);

	$settings['style_formats'] = json_encode( array_merge( $style_formats, $style_formats_original ) );

	return $settings;

}
add_filter( 'tiny_mce_before_init', 'custom_tinymce_styles', 100 );