WordPress/wp-admin/menu-header.php

<?php
/**
 * Displays Administration Menu.
 *
 * @package WordPress
 * @subpackage Administration
 */

/**
 * The current page.
 *
 * @global string $self
 * @name $self
 * @var string
 */
$self = preg_replace('|^.*/wp-admin/|i', '', $_SERVER['PHP_SELF']);
$self = preg_replace('|^.*/plugins/|i', '', $self);

global $menu, $submenu, $parent_file; //For when admin-header is included from within a function.

get_admin_page_parent();

/**
 * Display menu.
 *
 * @access private
 * @since 2.7.0
 *
 * @param array $menu
 * @param array $submenu
 * @param bool $submenu_as_parent
 */
function _wp_menu_output( &$menu, &$submenu, $submenu_as_parent = true ) {
	global $self, $parent_file, $submenu_file, $plugin_page, $pagenow;

	$first = true;
	// 0 = name, 1 = capability, 2 = file, 3 = class, 4 = id, 5 = icon src
	foreach ( $menu as $key => $item ) {
		$admin_is_parent = false;
		$class = array();
		if ( $first ) {
			$class[] = 'wp-first-item';
			$first = false;
		}
		if ( !empty($submenu[$item[2]]) )
			$class[] = 'wp-has-submenu';

		if ( ( $parent_file && $item[2] == $parent_file ) || strcmp($self, $item[2]) == 0 ) {
			if ( !empty($submenu[$item[2]]) )
				$class[] = 'wp-has-current-submenu wp-menu-open';
			else
				$class[] = 'current';
		}

		if ( isset($item[4]) && ! empty($item[4]) )
			$class[] = $item[4];

		$class = $class ? ' class="' . join( ' ', $class ) . '"' : '';
		$id = isset($item[5]) && ! empty($item[5]) ? ' id="' . $item[5] . '"' : '';
		$img = isset($item[6]) && ! empty($item[6]) ? '<img class="wp-menu-image" src="' . $item[6] . '" alt="" />' : '';
		$toggle = '<div class="wp-menu-toggle"><br /></div>';

		echo "\n\t<li$class$id>";

		if ( false !== strpos($class, 'wp-menu-separator') ) {
			echo '<br />';
		} elseif ( $submenu_as_parent && !empty($submenu[$item[2]]) ) {
			$submenu[$item[2]] = array_values($submenu[$item[2]]);  // Re-index.
			$menu_hook = get_plugin_page_hook($submenu[$item[2]][0][2], $item[2]);
			if ( file_exists(WP_PLUGIN_DIR . "/{$submenu[$item[2]][0][2]}") || !empty($menu_hook)) {
				$admin_is_parent = true;
				echo "$img$toggle<a href='admin.php?page={$submenu[$item[2]][0][2]}'$class>{$item[0]}</a>";
			} else {
				echo "\n\t$img$toggle<a href='{$submenu[$item[2]][0][2]}'$class>{$item[0]}</a>";
			}
		} else if ( current_user_can($item[1]) ) {
			$menu_hook = get_plugin_page_hook($item[2], 'admin.php');
			if ( file_exists(WP_PLUGIN_DIR . "/{$item[2]}") || !empty($menu_hook) ) {
				$admin_is_parent = true;
				echo "\n\t$img$toggle<a href='admin.php?page={$item[2]}'$class>{$item[0]}</a>";
			} else {
				echo "\n\t$img$toggle<a href='{$item[2]}'$class>{$item[0]}</a>";
			}
		}

		if ( !empty($submenu[$item[2]]) ) {
			echo "\n\t<ul class='wp-submenu'><li class='wp-submenu-head' style='display:none;'>{$item[0]}</li>";
			$first = true;
			foreach ( $submenu[$item[2]] as $sub_key => $sub_item ) {
				if ( !current_user_can($sub_item[1]) )
					continue;

				$class = array();
				if ( $first ) {
					$class[] = 'wp-first-item';
					$first = false;
				}
				if ( isset($submenu_file) ) {
					if ( $submenu_file == $sub_item[2] )
						$class[] = 'current';
				// If plugin_page is set the parent must either match the current page or not physically exist.
				// This allows plugin pages with the same hook to exist under different parents.
				} else if ( (isset($plugin_page) && $plugin_page == $sub_item[2] && (!file_exists($item[2]) || ($item[2] == $self))) || (!isset($plugin_page) && $self == $sub_item[2]) ) {
					$class[] = 'current';
				}

				$class = $class ? ' class="' . join( ' ', $class ) . '"' : '';

				$menu_hook = get_plugin_page_hook($sub_item[2], $item[2]);

				if ( file_exists(WP_PLUGIN_DIR . "/{$sub_item[2]}") || ! empty($menu_hook) ) {
					// If admin.php is the current page or if the parent exists as a file in the plugins or admin dir
					$parent_exists = (!$admin_is_parent && file_exists(WP_PLUGIN_DIR . "/{$item[2]}") && !is_dir(WP_PLUGIN_DIR . "/{$item[2]}") ) || file_exists($item[2]);
					if ( $parent_exists )
						echo "<li$class><a href='{$item[2]}?page={$sub_item[2]}'$class>{$sub_item[0]}</a></li>";
					elseif ( 'admin.php' == $pagenow || !$parent_exists )
						echo "<li$class><a href='admin.php?page={$sub_item[2]}'$class>{$sub_item[0]}</a></li>";
					else
						echo "<li$class><a href='{$item[2]}?page={$sub_item[2]}'$class>{$sub_item[0]}</a></li>";
				} else {
					echo "<li$class><a href='{$sub_item[2]}'$class>{$sub_item[0]}</a></li>";
				}
			}
			echo "</ul>";
		}
		echo "</li>";
	}
}

?>

<ul id="adminmenu">

<?php

_wp_menu_output( $menu, $submenu );
do_action( 'adminmenu' );

?>
</ul>