WordPress函数：get_children （获取子对象）

Description【描述】

get_children() retrieves attachments, revisions, or sub-Pages, possibly by post parent. It works similarly to get_posts().【get_children()  可以根据父级文章检索附件、修订版本 或者 子页面。它的作用和 get_posts() 相似。】

Synopsis【简介】

array $children =& get_children( mixed $args = "", constant $output = OBJECT);

Return values【返回值】

Returns an associative array of posts (of variable type set by $outputparameter) with post IDs as array keys, or an empty array if no posts are found.【返回一组以文章ID作为数组值的关联文章（根据 $outputparameter 的变量类型设置）；如果不存在文章，将返回一个空数组】

Prior to Version 2.9, the return value would be false when no children found.【在版本 2.9 之前，如果不存在子对象，返回的值将是错误的】

Default parameters (Version 2.7)【默认参数（版本 2.7）】

$defaults = array( 
    'post_parent' => 0,
    'post_type'   => 'any', 
    'numberposts' => -1,
    'post_status' => 'any'
);

Parameters【参数】

See get_posts() for a full list of parameters.【要查看所有的参数，请阅读 get_posts() 】

$args

(mixed) Passing a query-style string or array sets several parameters (below). Passing an integer post ID or a post object will retrieve children of that post; passing an empty value will retrieve children of the current post or Page. 【(mixed)通过 一个查询类型的字符串或数组 设置（下面）几个参数。通过一个 整数 的文章 ID 或 文章对象 将检索到那篇文章的子对象；过一个 空值 将检索到 当前文章或页面 的子对象。】

$args[‘numberposts’]

(integer) Number of child posts to retrieve. Optional; default: -1 (unlimited) 【（整数）要检索的子文章的数量。可选，默认：-1（不限制）】

$args[‘post_parent’]

(integer) Pass the ID of a post or Page to get its children. Pass 0 to get attachments without parent. Passnull to get any child regardless of parent. Optional; default: 0 (no parent) 【（整数）通过文章或页面的 ID 来检索它的子对象。通过 0 获取不包含父级的附件。通过 null 获取任何父级的子对象。可选，默认：0 （不包含父级）】

$args[‘post_type’]

(string) Any value from post_type column of the posts table, such as attachment, page, or revision; or the keyword any. Default: any 【（字符串）来自文章表的 post_type（文章类型） 那一栏的任何值，比如 附件、页面、修订版本 或 任何关键字。默认：any】

$args[‘post_status’]

(string) Any value from the post_status column of the wp_posts table, such as publish, draft, or inherit; or the keyword any. Default: any 【（字符串）来自 wp_posts 表的 post_status（文章状态） 那一栏的任何值，比如 已发布、草稿、继承 或任何关键字。默认：any】

$args[‘post_mime_type’]

(string) A full or partial mime-type, e.g. image, video, video/mp4, which is matched against a post’s post_mime_type field 【（字符串）一个完整的或部分的 mime-type，比如 图像、视频、视频/MP4，它和一篇文章的 post_mime_type 字段相匹配 】

$output

(constant) Variable type of the array items returned by the function: one of OBJECT, ARRAY_A, ARRAY_N. Optional; default: OBJECT【（常量）由该函数返回的数组项的变量类型：OBJECT, ARRAY_A, ARRAY_N 的其中一种。可选，默认：OBJECT】

Examples【例子】

If you just want to get or display attachments, it’s probably a little easier to use get_posts() instead.【如果你想要获取或显示附件，可能使用 get_posts() 会更加容易。】

$images =& get_children( 'post_type=attachment&post_mime_type=image' );

$videos =& get_children( 'post_type=attachment&post_mime_type=video/mp4' );

if ( empty($images) ) {
	// no attachments here【这里没有附件】
} else {
	foreach ( $images as $attachment_id => $attachment ) {
		echo wp_get_attachment_image( $attachment_id, 'full' );
	}
}

//  If you don't need to handle an empty result:【如果你没必要处理一个空的结果：】

foreach ( (array) $videos as $attachment_id => $attachment ) {
	echo wp_get_attachment_link( $attachment_id );
}

Show the first image associated with the post【展示与文章相关的第一张图片】

This function retrieves the first image associated with a post【下面的函数将检索与一篇文章相关的第一张图片】

function echo_first_image ($postID)
{					
	$args = array(
	'numberposts' => 1,
	'order'=> 'ASC',
	'post_mime_type' => 'image',
	'post_parent' => $postID,
	'post_status' => null,
	'post_type' => 'attachment'
	);
	
	$attachments = get_children( $args );
	
	//print_r($attachments);
	
	if ($attachments) {
		foreach($attachments as $attachment) {
			$image_attributes = wp_get_attachment_image_src( $attachment->ID, 'thumbnail' )  ? wp_get_attachment_image_src( $attachment->ID, 'thumbnail' ) : wp_get_attachment_image_src( $attachment->ID, 'full' );
				
			echo '<img src="'.wp_get_attachment_thumb_url( $attachment->ID ).'" class="current">';
			
		}
	}
}

Show the first image associated with the post and re-key the array【展示与文章 和 重新输入的数组 相关的第一张图片】

In the example above, a primary array is keyed with the image ID (the exact thing which is being sought – since we don’t know it how are we supposed to access it?). The code below provides an easier handle for the image information: the array $child_image. Should be used in the loop.【在上面的例子中，一个最初的数组输入的是图片的 ID（正是要寻求的东西——因为我们不知道我们应该如何访问它）。下面的代码将提供一种更容易的处理图片信息的方式：数组 $child_image。它应该在循环中使用。】

$args = array(
	'numberposts' => 1,
	'order'=> 'DESC',
	'post_mime_type' => 'image',
	'post_parent' => $post->ID,
	'post_type' => 'attachment'
	);

$get_children_array = get_children($args,ARRAY_A);  //returns Array ( [$image_ID]... 
$rekeyed_array = array_values($get_children_array);
$child_image = $rekeyed_array[0];  


print_r($child_image);  	//输出 $child_image 数组的内容
echo $child_image['ID'];   	//输出 $child_image 的ID

Change Log【更新日志】

Since: 2.0.0

Source File【源文件】

get_children() 在 wp-includes/post.php 文件中。

Related【相关函数】

get_children() calls get_posts(), which calls $WP_Query->get_posts().

wp_get_attachment_link(), get_page_children()

参考资料：http://codex.wordpress.org/Function_Reference/get_children