How to create a theme navigation menu in WordPress (2)

I introduced you to "How to create a theme navigation menu in WordPress (1)". This article will continue to introduce you to how to create a theme navigation menu in WordPress. I hope it will be helpful to you!

The previous tutorial talked about how to use WordPress’s built-in functions to create navigation menus, but the HTML codes generated by these functions are fixed, making it difficult for you to define navigation. The HTML code for the menu. This article will introduce you to a few freer ways to create navigation menus that can be used for more than just navigation menus. Of course, this article only provides you with an idea to solve the problem. It is not a tutorial like a recipe. Once you read it and copy it, you can use it in your project.

1. Use get_terms() to get the category list

Use get_terms() to get your article categories, link categories and customizations Categories, etc., passing the corresponding parameters to get_terms() can return you an object array. This array is all the categories you want. The following is the function prototype of get_terms():

<?php get_terms( $taxonomies, $args ) ?>

$taxonomies:
This parameter is the classification category you want to obtain. Optional values ​​include: "category", "link_category", "my_taxonomy", which respectively represent article classification, link classification and Your customized classification, where my_taxonomy is your customized classification name.

$args:
This parameter is the filtering parameter of the category, used to control the acquisition of the category you want to obtain, including how many categories you want to obtain, how to sort, and the parent category And whether to output empty categories, etc. For details, please refer to WordPress official documentation: Function Reference/get terms, or refer to the brief translation in Chinese: Common functions-get_terms()

The following is an example of using this function. Here, an unordered list in the form of

• ..
..

of all article categories will be displayed. Of course, we can Think of it as a menu:

<ul id="menu">		
<?php
	// 获取分类
	$terms = get_terms(&#39;category&#39;, &#39;orderby=name&hide_empty=0&#39; );

	// 获取到的分类数量
	$count = count($terms);
	if($count > 0){
		// 循环输出所有分类信息
		foreach ($terms as $term) {
			echo &#39;<li><a href="&#39;.get_term_link($term, $term->slug).&#39;" title="&#39;.$term->name.&#39;">&#39;.$term->name.&#39;</a></li>&#39;;
		}
 	}
?>		
</ul>

The get_terms() function returns an object array $terms. We first determine whether the array is empty. If it is empty, it means that no category has been obtained. If If it is not empty then you can output the classification. Each array item of $terms is an object. The meanings of some object attributes are: slug: category abbreviation, name: category name, term_id: category id. As shown in the above code, you can get the attribute value of the object through $term->name.

2. Use the method of reading the database to obtain the classification list

If you know the WordPress database, you can find that WordPress classification information is stored in wp_terms and wp_term_taxonomy. In the table, wp_terms stores basic information (including article classification, article tags, link classification, etc.), and wp_term_taxonomy is used to store further descriptions (used to store descriptions, distinguish categories and tags, etc.). We can use SQL to get the list of categories we want from these two tables:

<ul id="menu">		
<?php 
	$cats = $wpdb->get_results("SELECT {$wpdb->prefix}terms.term_id, name
							FROM {$wpdb->prefix}term_taxonomy, {$wpdb->prefix}terms
							WHERE {$wpdb->prefix}term_taxonomy.term_id = {$wpdb->prefix}terms.term_id
							AND taxonomy = &#39;category&#39;");
							
	if($cats) {
		foreach($cats as $cat) {
			echo &#39;<li><a href="&#39;.get_category_link($cat->term_id).&#39;" title="&#39;.$cat->name.&#39;">&#39;.$cat->name.&#39;</a></li>&#39;;
		}
 	}
?>		
</ul>

3. How to get the id of the current category

Sometimes we need to make a sub-navigation, such as the human resources navigation on the left of http://www.nashowgroup.com/?p=58&lang=zh. This navigation can be any item, such as the current category subcategories under or articles under the current category, etc. So the first question is, how to get the ID of the current category so that we can take the next step.

Get the id of the current category on the category page:

if ( is_category() ) {
	$cat_id = get_query_var('cat');
}

Get the first category of the article on the article page:

$cats = get_the_category();
if($cats)
    $cat_id = $cats[0]->cat_ID;

四、子导航的制作

上面我们讲解了如何获取当前分类的id，下面我们来讲讲如何制作子导航。首先，我们来制作一个当前分类下子分类的子导航，这里用到wp_list_categories()来列出子分类，当然你可以用我前面介绍的两种方法来获取分类。：

<ul>
<?php
// 这里我们用到上面获取到的$cat_id，获取该分类下的所有子分类
wp_list_categories(&#39;orderby=name&hide_empty=0&child_of=&#39; . $cat_id);
?> 
</ul>

如果你的网站规模比较小，一个分类下的文章也不多，那么你可以在子导航中列出这个分类下的所有文章：

<ul>
	<?php
		global $wp_query;

		$query = array ( &#39;cat&#39; => $cat_id, &#39;orderby&#39; => title, &#39;order&#39;=> ASC ); 
		$queryObject = new WP_Query($query); 

		if ($queryObject->have_posts()) :
			while ($queryObject->have_posts()) :
			    $queryObject->the_post();
	?>
	<li><a <?php if($post->ID == $wp_query->post->ID) echo &#39;class="chose"&#39;; ?> href="<?php the_permalink() ?>"><?php the_title(); ?></a></li>
	<?php endwhile; wp_reset_postdata(); endif; ?>
</ul>

以上代码中用到了WP_Query来获取文章列表，该对象的使用方法，可以参考WordPress的官方文档：Class Reference/WP Query和Function Reference/query posts。class="chose"用于高亮当前文章的菜单项，css规则你可以自己定义。

五、页面page的获取

WordPress的页面page可以通过wp_list_pages()来列出，不过这个函数输出的HTML都是固定的，如果你想要自定义这些HTML，可以使用get_pages()来获取页面列表，代码示例如下：

<ul id="menu">
$mypages = get_pages();

if(count($mypages) > 0) {
    foreach($mypages as $page) {
        echo &#39;<li><a href="&#39;.get_page_link($page->ID).&#39;" title="&#39;.$page->post_title.&#39;">&#39;.$page->post_title.&#39;</a></li>&#39;;
    }
}
else {
    echo &#39;<li><a href="#">没有页面</a></li>&#39;;
}
</ul>

-- 完 --

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