[WordPress]公開側からメディアを追加する

公開側で画像をアップロードして任意の投稿のアイキャッチに設定したい場合などに。

function insert_attachment($media, $post_id, $old_id, $title, $caption) {
	require_once(ABSPATH.'wp-admin/includes/image.php');
	require_once(ABSPATH.'wp-admin/includes/file.php');
	require_once(ABSPATH.'wp-admin/includes/media.php');
	$wp_upload_dir = wp_upload_dir();
	$post_data = [
			'post_title' => $title,
			'post_content' => $caption,
			'guid' => $wp_upload_dir['url'].'/'.basename($media)
	];
	if ( $post_id && $thumbnail_id = media_handle_upload($media, $post_id, $post_data) ) {
		if ( $old_id ) {//旧アイキャッチを削除
			wp_delete_attachment($old_id, true);
		}
		//アイキャッチ設定
		set_post_thumbnail($post_id, $thumbnail_id);
		return true;
	}
	return false;
}

$media = 'file';
insert_attachment($media, $post_id, $old_id, $title, $caption);

$mediaはtype='file'のname

<form method="post" enctype="multipart/form-data">
	<input type="file" name="file">
</form>