WordPress - Menu with Bootstrap 4 Navbar

index.php

<?php
	$menu_items = wp_get_nav_menu_items('Menu Principal'); // PEGA TODOS OS ITENS DO Menu Principal
	$menu_mobile = array();
	foreach ( $menu_items as $key => $value ) { // SEPARA OS ITENS EM SUBMENUS
		if ( !is_array( $menu_mobile[$value->menu_item_parent] ) ) {
			$menu_mobile[$value->menu_item_parent] = array();
		}
		array_push( $menu_mobile[$value->menu_item_parent], $value );
	}
?>

<nav class="navbar navbar-expand-lg navbar-light bg-light fixed-top">
	<a class="navbar-brand" href="<?php echo home_url() ?>" class="logo">Logo</a>
	<button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarNav" aria-controls="navbarNav" aria-expanded="false" aria-label="Toggle navigation">
		<span class="navbar-toggler-icon"></span>
	</button>
	<div class="collapse navbar-collapse" id="navbarNav">
		<ul class="navbar-nav">
			<?php foreach ( $menu_mobile[0] as $key => $value ): ?>
				<li class="nav-item">
					<a class="nav-link" href="<?php echo $value->url ?>"><?php echo $value->title ?></a>

					<?php // PRIMEIRO NÍVEL DE SUBMENU ?>
						<?php if ( count( $menu_mobile[ $value->ID ] ) > 0 ): ?>
						<ul class="navbar-nav">
							<?php foreach ( $menu_mobile[ $value->ID ] as $key2 => $value2 ): ?>
							<li class="nav-item">
								<a class="nav-link" href="<?php echo $value2->url ?>"><?php echo $value2->title ?></a>

								<?php // SEGUNDO NÍVEL DE SUBMENU ?>
								<?php if ( count( $menu_mobile[ $value->ID ] ) > 0 ): ?>
										<ul class="navbar-nav">
											<?php foreach ( $menu_mobile[ $value->ID ] as $key2 => $value2 ): ?>
											<li class="nav-item"><a class="nav-link" href="<?php echo $value2->url ?>"><?php echo $value2->title ?></a></li>
											<?php endforeach ?>
										</ul>
										<?php endif ?>
								<?php // SEGUNDO NÍVEL DE SUBMENU ?>

							</li>
							<?php endforeach ?>
						</ul>
						<?php endif ?>
					<?php // PRIMEIRO NÍVEL DE SUBMENU ?>

				</li>
			<?php endforeach ?>
		</ul>
	</div>
</nav>