Add button to TinyMCE

tiny_mce.php

<?php
/**
 * Registers an editor stylesheet for the theme.
 */
function lm_theme_add_editor_styles() {
    add_editor_style( get_stylesheet_directory_uri().'/editor-style.css?ver='.filemtime(get_stylesheet_directory().'/editor-style.css')); //by default editor-style.css
}
add_action( 'admin_init', 'lm_theme_add_editor_styles' );


/**
 * Add "Styles" drop-down to the second row of buttons
 */
add_filter( 'mce_buttons_2', 'tuts_mce_editor_buttons' );

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

// Callback function to filter the MCE settings
function lm_mce_before_init_insert_formats( $settings ) {  
	// Define the style_formats array
	$style_formats = array(  
		// Each array child is a format with it's own settings
		array(  
			'title' => 'Big Title',  
			'block' => 'h3',  
			'classes' => 'btitle',
			
		),  
		array(  
			'title' => 'Small Title',  
			'block' => 'p',  
			'classes' => 'sline',
		),
		array(  
			'title' => 'Video Link',  
			'selector' => 'a',  
			'exact' => true, 
			'classes' => 'svideo fancyboxforwp',
		),
		array(  
			'title' => 'Button',  
			'selector' => 'a', 
			'exact' => true, 
			'classes' => 'btn',
		),	
	);  
	if ( isset( $settings['style_formats'] ) ) {
		$orig_style_formats = json_decode( $settings['style_formats'], true );
		$style_formats      = array_merge( $orig_style_formats, $style_formats );
	}

	$settings['style_formats'] = json_encode( $style_formats );
	
	return $settings;  
  
} 
// Attach callback to 'tiny_mce_before_init' 
add_filter( 'tiny_mce_before_init', 'lm_mce_before_init_insert_formats' );