描述：

删除文章/页面的自定义栏目(字段)

用法：

 <?php delete_post_meta($post_id, $meta_key, $meta_value); ?> 

参数：

$post_id

(integer) (必填) 要从中删除字段的文章的ID。

默认值: None

$meta_key

(string) (必填) 要删除的字段的键。

默认值: None

$meta_value

(mixed) (可选) 要删除的字段的值。这用于区分具有相同键的多个字段。如果留空，则具有给定键的所有字段都将被删除。

默认值: Empty

示例：

<?php delete_post_meta(76, 'my_key', 'Steve'); ?>

源文件：

/**
 * Remove metadata matching criteria from a post.
 *
 * You can match based on the key, or key and value. Removing based on key and
 * value, will keep from removing duplicate metadata with the same key. It also
 * allows removing all metadata matching key, if needed.
 *
 * @since 1.5.0
 *
 * @param int    $post_id    Post ID.
 * @param string $meta_key   Metadata name.
 * @param mixed  $meta_value Optional. Metadata value. Must be serializable if
 *                           non-scalar. Default empty.
 * @return bool True on success, false on failure.
 */
function delete_post_meta( $post_id, $meta_key, $meta_value = '' ) {
	// Make sure meta is added to the post, not a revision.
	if ( $the_post = wp_is_post_revision($post_id) )
		$post_id = $the_post;

	return delete_metadata('post', $post_id, $meta_key, $meta_value);
}