Sindbad~EG File Manager

<?php

namespace RealPress\Controllers;

class MenuController {

	public function __construct() {
		add_filter( 'nav_menu_css_class', array( $this, 'modify_menu_class' ), 10, 2 );
	}

	public function modify_menu_class( $classes, $item ) {
		$object_id = get_post_meta( $item->ID, '_menu_item_object_id', true );

		if ( empty( $object_id ) || $object_id !== get_option( 'page_for_posts' ) ) {
			return $classes;
		}

		if ( is_singular( 'post' ) ) {
			return $classes;
		}

		return array_diff( $classes, array( 'current_page_parent' ) );
	}
}