如何修复WordPress中get_the_terms()引发的foreach()参数类型警告？

问题原因 #

你遇到的Warning: foreach() argument must be of type array|object, bool警告，是因为代码中get_the_terms( $product->get_id(), 'product_tag' )这个调用：当产品没有关联任何产品标签，或者查询过程出现错误时，该函数会返回false（甚至是WP_Error对象），而foreach只能遍历数组或对象，直接遍历布尔值就会触发警告。

修复方案 #

在遍历$tags之前，先判断它是否为有效可遍历的类型，同时排除错误对象。具体要在foreach ($tags as $tag)前添加判断条件：

if ( $tags && ! is_wp_error( $tags ) ) {
    foreach ($tags as $tag) {
        // 原有的标签处理代码
    }
}

修改后的完整代码 #

function custom_product_tag_cloud_func() {
   if (is_shop()) {
       $args= array(
     'smallest' => 13,
     'largest' => 13,
     'taxonomy' => 'product_tag',
     'unit' => 'px',
     'number' => 10,
     'format' => 'flat',
     'separator' => " ",
     'orderby' => 'count',
     'order' => 'DESC',
     'show_count' => 0,
     'number' => 0,
       );
       echo'<div class="widget_product_tag_cloud"><span class="gamma widget-title"></span><div class="tagcloud"><ul class="wp-tag-cloud">';
       wp_tag_cloud($args);
       echo '</ul></div></div>';
   }
    global $wp;
    $current_slug = add_query_arg( array(), $wp->request );
    if(strpos($current_slug, '/') !== false) {
        $newtest = explode('/', $current_slug);
        $current_slug = array_pop($newtest);
    } 
    $args = array(
        'category' => array( $current_slug ),
        'limit' => -1,
    );
    $products = wc_get_products( $args );
    $tags_objects = array();
    foreach ($products as $product) {
        $tags = get_the_terms( $product->get_id(), 'product_tag' );
        // 添加判断，确保$tags是有效可遍历的类型
        if ( $tags && ! is_wp_error( $tags ) ) {
            foreach ($tags as $tag) { 
                $slug = $tag->slug;
                $cat_slug = add_query_arg( array(), $wp->request );
                $tag->link = get_term_link( $tag ); //get_site_url()."/".$cat_slug."?product_tag=".$slug;
                array_push($tags_objects,$tag);
            }
        }
    }
    $tags_objects = array_unique($tags_objects, SORT_REGULAR);
    $args = array(
        'smallest' => 13,
        'largest' => 13,
           'number' => 10,
        'format' => 'flat',
        'separator' => " ",
        'orderby' => 'count',
        'order' => 'DESC',
        'unit' => 'px',
        'show_count' => 0,
        'number' => 0,
    );
    $tag_cloud = wp_generate_tag_cloud($tags_objects,$args);
    if(is_product_category()){
        echo'<div class="widget_product_tag_cloud"><span class="gamma widget-title"></span><div class="tagcloud"><ul class="wp-tag-cloud">';
        echo $tag_cloud;
        echo '</ul></div></div>';
    }
} 

内容的提问来源于stack exchange，提问作者Lgane