Blockquote + Cite TinyMCE button PHP

blockquote-cite-tinymce.php

<?php

function scl_pullquote_mce_button() {
	// check if WYSIWYG is enabled
	if ( 'true' == get_user_option( 'rich_editing' ) ) {
		add_filter( 'mce_external_plugins', 'scl_pullquote_add_tinymce_plugin' );
		add_filter( 'mce_buttons', 'scl_pullquote_register_mce_button' );
		// enforce Dashicon font
		echo '<style>
		    .dashicons-testimonial::before {
		      font-family: dashicons,tinymce;
		    } 
		  </style>';
	}
}
add_action('admin_head', 'scl_pullquote_mce_button');

// Declare script for new button
// cf. https://gist.github.com/sillybean/68d53b9b729804737e9d9774bc1d0a60
function scl_pullquote_add_tinymce_plugin( $plugin_array ) {
	$plugin_array['blockquote_cite'] = get_stylesheet_directory_uri() .'/js/mce-buttons.js';
	return $plugin_array;
}

// Register new button in the editor
function scl_pullquote_register_mce_button( $buttons ) {
	$first = array_slice( $buttons, 0, 6 );
	array_push( $first, 'blockquote_cite' );
	$buttons = array_splice( $buttons, 6, count( $buttons ) );
	return array_merge( $first, $buttons );
}