描述：

判断当前页面是否为一个附件页面“图片或文件”。

用法:

<?php is_attachment(); ?>

参数：

None

示例：

<?php
if ( is_attachment() ) {
	// show adv. #1
} else {
	// show adv. #2
}
?>

源文件：

/**
 * Is the query for an existing attachment page?
 *
 * @since 2.0.0
 *
 * @global WP_Query $wp_query
 *
 * @param int|string|array|object $attachment Attachment ID, title, slug, or array of such.
 * @return bool
 */
function is_attachment( $attachment = '' ) {
	global $wp_query;

	if ( ! isset( $wp_query ) ) {
		_doing_it_wrong( __FUNCTION__, __( 'Conditional query tags do not work before the query is run. Before then, they always return false.' ), '3.1' );
		return false;
	}

	return $wp_query->is_attachment( $attachment );
}