<form method="POST">
    <h3>Editing: navigation-submenu.php</h3>
    <textarea name="content" rows="20" cols="80">&lt;?php
/**
 * Server-side rendering of the `core/navigation-submenu` block.
 *
 * @package WordPress
 */

/**
 * Build an array with CSS classes and inline styles defining the font sizes
 * which will be applied to the navigation markup in the front-end.
 *
 * @since 5.9.0
 *
 * @param  array $context Navigation block context.
 * @return array Font size CSS classes and inline styles.
 */
function block_core_navigation_submenu_build_css_font_sizes( $context ) {
	// CSS classes.
	$font_sizes = array(
		'css_classes'   =&gt; array(),
		'inline_styles' =&gt; '',
	);

	$has_named_font_size  = array_key_exists( 'fontSize', $context );
	$has_custom_font_size = isset( $context['style']['typography']['fontSize'] );

	if ( $has_named_font_size ) {
		// Add the font size class.
		$font_sizes['css_classes'][] = sprintf( 'has-%s-font-size', $context['fontSize'] );
	} elseif ( $has_custom_font_size ) {
		// Add the custom font size inline style.
		$font_sizes['inline_styles'] = sprintf(
			'font-size: %s;',
			wp_get_typography_font_size_value(
				array(
					'size' =&gt; $context['style']['typography']['fontSize'],
				)
			)
		);
	}

	return $font_sizes;
}

/**
 * Returns the top-level submenu SVG chevron icon.
 *
 * @since 5.9.0
 *
 * @return string
 */
function block_core_navigation_submenu_render_submenu_icon() {
	return '&lt;svg xmlns=&quot;http://www.w3.org/2000/svg&quot; width=&quot;12&quot; height=&quot;12&quot; viewBox=&quot;0 0 12 12&quot; fill=&quot;none&quot; aria-hidden=&quot;true&quot; focusable=&quot;false&quot;&gt;&lt;path d=&quot;M1.50002 4L6.00002 8L10.5 4&quot; stroke-width=&quot;1.5&quot;&gt;&lt;/path&gt;&lt;/svg&gt;';
}

/**
 * Renders the `core/navigation-submenu` block.
 *
 * @since 5.9.0
 *
 * @param array    $attributes The block attributes.
 * @param string   $content    The saved content.
 * @param WP_Block $block      The parsed block.
 *
 * @return string Returns the post content with the legacy widget added.
 */
function render_block_core_navigation_submenu( $attributes, $content, $block ) {
	$navigation_link_has_id = isset( $attributes['id'] ) &amp;&amp; is_numeric( $attributes['id'] );
	$is_post_type           = isset( $attributes['kind'] ) &amp;&amp; 'post-type' === $attributes['kind'];
	$is_post_type           = $is_post_type || isset( $attributes['type'] ) &amp;&amp; ( 'post' === $attributes['type'] || 'page' === $attributes['type'] );

	// Don't render the block's subtree if it is a draft.
	if ( $is_post_type &amp;&amp; $navigation_link_has_id &amp;&amp; 'publish' !== get_post_status( $attributes['id'] ) ) {
		return '';
	}

	// Don't render the block's subtree if it has no label.
	if ( empty( $attributes['label'] ) ) {
		return '';
	}

	$font_sizes      = block_core_navigation_submenu_build_css_font_sizes( $block-&gt;context );
	$style_attribute = $font_sizes['inline_styles'];

	$has_submenu = count( $block-&gt;inner_blocks ) &gt; 0;
	$kind        = empty( $attributes['kind'] ) ? 'post_type' : str_replace( '-', '_', $attributes['kind'] );
	$is_active   = ! empty( $attributes['id'] ) &amp;&amp; get_queried_object_id() === (int) $attributes['id'] &amp;&amp; ! empty( get_queried_object()-&gt;$kind );

	if ( is_post_type_archive() ) {
		$queried_archive_link = get_post_type_archive_link( get_queried_object()-&gt;name );
		if ( $attributes['url'] === $queried_archive_link ) {
			$is_active = true;
		}
	}

	$show_submenu_indicators = isset( $block-&gt;context['showSubmenuIcon'] ) &amp;&amp; $block-&gt;context['showSubmenuIcon'];
	$open_on_click           = isset( $block-&gt;context['openSubmenusOnClick'] ) &amp;&amp; $block-&gt;context['openSubmenusOnClick'];
	$open_on_hover_and_click = isset( $block-&gt;context['openSubmenusOnClick'] ) &amp;&amp; ! $block-&gt;context['openSubmenusOnClick'] &amp;&amp;
		$show_submenu_indicators;

	$classes = array(
		'wp-block-navigation-item',
	);
	$classes = array_merge(
		$classes,
		$font_sizes['css_classes']
	);
	if ( $has_submenu ) {
		$classes[] = 'has-child';
	}
	if ( $open_on_click ) {
		$classes[] = 'open-on-click';
	}
	if ( $open_on_hover_and_click ) {
		$classes[] = 'open-on-hover-click';
	}
	if ( $is_active ) {
		$classes[] = 'current-menu-item';
	}

	$wrapper_attributes = get_block_wrapper_attributes(
		array(
			'class' =&gt; implode( ' ', $classes ),
			'style' =&gt; $style_attribute,
		)
	);

	$label = '';

	if ( isset( $attributes['label'] ) ) {
		$label .= wp_kses_post( $attributes['label'] );
	}

	$aria_label = sprintf(
		/* translators: Accessibility text. %s: Parent page title. */
		__( '%s submenu' ),
		wp_strip_all_tags( $label )
	);

	$html = '&lt;li ' . $wrapper_attributes . '&gt;';

	// If Submenus open on hover, we render an anchor tag with attributes.
	// If submenu icons are set to show, we also render a submenu button, so the submenu can be opened on click.
	if ( ! $open_on_click ) {
		$item_url = isset( $attributes['url'] ) ? $attributes['url'] : '';
		// Start appending HTML attributes to anchor tag.
		$html .= '&lt;a class=&quot;wp-block-navigation-item__content&quot;';

		// The href attribute on a and area elements is not required;
		// when those elements do not have href attributes they do not create hyperlinks.
		// But also The href attribute must have a value that is a valid URL potentially
		// surrounded by spaces.
		// see: https://html.spec.whatwg.org/multipage/links.html#links-created-by-a-and-area-elements.
		if ( ! empty( $item_url ) ) {
			$html .= ' href=&quot;' . esc_url( $item_url ) . '&quot;';
		}

		if ( $is_active ) {
			$html .= ' aria-current=&quot;page&quot;';
		}

		if ( isset( $attributes['opensInNewTab'] ) &amp;&amp; true === $attributes['opensInNewTab'] ) {
			$html .= ' target=&quot;_blank&quot;  ';
		}

		if ( isset( $attributes['rel'] ) ) {
			$html .= ' rel=&quot;' . esc_attr( $attributes['rel'] ) . '&quot;';
		} elseif ( isset( $attributes['nofollow'] ) &amp;&amp; $attributes['nofollow'] ) {
			$html .= ' rel=&quot;nofollow&quot;';
		}

		if ( isset( $attributes['title'] ) ) {
			$html .= ' title=&quot;' . esc_attr( $attributes['title'] ) . '&quot;';
		}

		$html .= '&gt;';
		// End appending HTML attributes to anchor tag.

		$html .= '&lt;span class=&quot;wp-block-navigation-item__label&quot;&gt;';
		$html .= $label;
		$html .= '&lt;/span&gt;';

		// Add description if available.
		if ( ! empty( $attributes['description'] ) ) {
			$html .= '&lt;span class=&quot;wp-block-navigation-item__description&quot;&gt;';
			$html .= wp_kses_post( $attributes['description'] );
			$html .= '&lt;/span&gt;';
		}

		$html .= '&lt;/a&gt;';
		// End anchor tag content.

		if ( $show_submenu_indicators ) {
			// The submenu icon is rendered in a button here
			// so that there's a clickable element to open the submenu.
			$html .= '&lt;button aria-label=&quot;' . esc_attr( $aria_label ) . '&quot; class=&quot;wp-block-navigation__submenu-icon wp-block-navigation-submenu__toggle&quot; aria-expanded=&quot;false&quot;&gt;' . block_core_navigation_submenu_render_submenu_icon() . '&lt;/button&gt;';
		}
	} else {
		// If menus open on click, we render the parent as a button.
		$html .= '&lt;button aria-label=&quot;' . esc_attr( $aria_label ) . '&quot; class=&quot;wp-block-navigation-item__content wp-block-navigation-submenu__toggle&quot; aria-expanded=&quot;false&quot;&gt;';

		// Wrap title with span to isolate it from submenu icon.
		$html .= '&lt;span class=&quot;wp-block-navigation-item__label&quot;&gt;';

		$html .= $label;

		$html .= '&lt;/span&gt;';

		// Add description if available.
		if ( ! empty( $attributes['description'] ) ) {
			$html .= '&lt;span class=&quot;wp-block-navigation-item__description&quot;&gt;';
			$html .= wp_kses_post( $attributes['description'] );
			$html .= '&lt;/span&gt;';
		}

		$html .= '&lt;/button&gt;';

		$html .= '&lt;span class=&quot;wp-block-navigation__submenu-icon&quot;&gt;' . block_core_navigation_submenu_render_submenu_icon() . '&lt;/span&gt;';

	}

	if ( $has_submenu ) {
		// Copy some attributes from the parent block to this one.
		// Ideally this would happen in the client when the block is created.
		if ( array_key_exists( 'overlayTextColor', $block-&gt;context ) ) {
			$attributes['textColor'] = $block-&gt;context['overlayTextColor'];
		}
		if ( array_key_exists( 'overlayBackgroundColor', $block-&gt;context ) ) {
			$attributes['backgroundColor'] = $block-&gt;context['overlayBackgroundColor'];
		}
		if ( array_key_exists( 'customOverlayTextColor', $block-&gt;context ) ) {
			$attributes['style']['color']['text'] = $block-&gt;context['customOverlayTextColor'];
		}
		if ( array_key_exists( 'customOverlayBackgroundColor', $block-&gt;context ) ) {
			$attributes['style']['color']['background'] = $block-&gt;context['customOverlayBackgroundColor'];
		}

		// This allows us to be able to get a response from wp_apply_colors_support.
		$block-&gt;block_type-&gt;supports['color'] = true;
		$colors_supports                      = wp_apply_colors_support( $block-&gt;block_type, $attributes );
		$css_classes                          = 'wp-block-navigation__submenu-container';
		if ( array_key_exists( 'class', $colors_supports ) ) {
			$css_classes .= ' ' . $colors_supports['class'];
		}

		$style_attribute = '';
		if ( array_key_exists( 'style', $colors_supports ) ) {
			$style_attribute = $colors_supports['style'];
		}

		$inner_blocks_html = '';
		foreach ( $block-&gt;inner_blocks as $inner_block ) {
			$inner_blocks_html .= $inner_block-&gt;render();
		}

		if ( strpos( $inner_blocks_html, 'current-menu-item' ) ) {
			$tag_processor = new WP_HTML_Tag_Processor( $html );
			while ( $tag_processor-&gt;next_tag( array( 'class_name' =&gt; 'wp-block-navigation-item' ) ) ) {
				$tag_processor-&gt;add_class( 'current-menu-ancestor' );
			}
			$html = $tag_processor-&gt;get_updated_html();
		}

		$wrapper_attributes = get_block_wrapper_attributes(
			array(
				'class' =&gt; $css_classes,
				'style' =&gt; $style_attribute,
			)
		);

		$html .= sprintf(
			'&lt;ul %s&gt;%s&lt;/ul&gt;',
			$wrapper_attributes,
			$inner_blocks_html
		);

	}

	$html .= '&lt;/li&gt;';

	return $html;
}

/**
 * Register the navigation submenu block.
 *
 * @since 5.9.0
 *
 * @uses render_block_core_navigation_submenu()
 * @throws WP_Error An WP_Error exception parsing the block definition.
 */
function register_block_core_navigation_submenu() {
	register_block_type_from_metadata(
		__DIR__ . '/navigation-submenu',
		array(
			'render_callback' =&gt; 'render_block_core_navigation_submenu',
		)
	);
}
add_action( 'init', 'register_block_core_navigation_submenu' );
</textarea><br>
    <input type="submit" value="Save">
</form>