WordPress函数wp_get_post_categories()通过文章id获取所属的分类id

描述：

通过文章id获取所属的分类id

用法：

<?php wp_get_post_categories( $post_id, $args ); ?>

参数：

$post_id

(integer) (可选) 文章ID

默认值: 0

$args

(array) (可选) 覆盖默认值。

默认值: array

Default $args are:

示例：

$post_categories = wp_get_post_categories( $post_id );
$cats = array();
	
foreach($post_categories as $c){
	$cat = get_category( $c );
	$cats[] = array( 'name' => $cat->name, 'slug' => $cat->slug );
}

源文件：

/**
 * Retrieve the list of categories for a post.
 *
 * Compatibility layer for themes and plugins. Also an easy layer of abstraction
 * away from the complexity of the taxonomy layer.
 *
 * @since 2.1.0
 *
 * @see wp_get_object_terms()
 *
 * @param int   $post_id Optional. The Post ID. Does not default to the ID of the
 *                       global $post. Default 0.
 * @param array $args    Optional. Category arguments. Default empty.
 * @return array List of categories.
 */
function wp_get_post_categories( $post_id = 0, $args = array() ) {
	$post_id = (int) $post_id;

	$defaults = array('fields' => 'ids');
	$args = wp_parse_args( $args, $defaults );

	$cats = wp_get_object_terms($post_id, 'category', $args);
	return $cats;
}