Add Background Color (Highlight) Option in WordPress Editor TinyMCE

tp-tinymce-background-color.php

<?php
/* Hook to init */
add_action( 'init', 'tp_editor_background_color' );
 
/**
 * Add TinyMCE Button
 */
function tp_editor_background_color()
{
	/* Add the button/option in second row */
	add_filter( 'mce_buttons_2', 'tp_editor_background_color_button', 1, 2 ); // 2nd row
}
 
/**
 * Modify 2nd Row in TinyMCE and Add Background Color After Text Color Option
 */
function tp_editor_background_color_button( $buttons, $id )
{
	/* Only add this for content editor, you can remove this line to activate in all editor instance */
	if ( 'content' != $id )
		return $buttons;

	/* Add the button/option after 4th item */
	array_splice( $buttons, 4, 0, 'backcolor' );

	return $buttons;
}