将foreach循环中的数组连接到嵌套数组的单个变量中

I'm trying to get a list of different image sizes in Wordpress. I think this is more of a php question though so I'm asking it here instead of on the wordpress forum.

Here is my code:

function ajax_get_latest_posts(){   
   $attachments = get_children(array('post_parent' => $post->ID,
                    'post_status' => 'inherit',
                    'post_type' => 'attachment',
                    'post_mime_type' => 'image',
                    'order' => 'ASC',
                    'orderby' => 'menu_order ID'));

   foreach($attachments as $att_id => $attachment) {
      $large_bg_url = wp_get_attachment_image_src($attachment->ID, 'background-large');
      $medium_bg_url = wp_get_attachment_image_src($attachment->ID, 'background-medium');
      $small_bg_url = wp_get_attachment_image_src($attachment->ID, 'background-small');
      $imagesizes .= array('background_large' => $large_bg_url[0], 'background_medium' => $medium_bg_url[0], 'background_small' => $small_bg_url[0]);
   }

   $allimagesizes = array($imagesizes);

   return $allimagesizes;
}

The above code does not work but hopefully shows what I'm trying to achieve. The problem is the concatenation of $imagesizes is not right. Below is the output I actually need to achieve but I cannot seem to figure out how to get this output from the foreach loop.

$allimagesizes = array(
   array(
      'background_large' => 'http://mydomain.com.au/wp-content/uploads/facade.jpg', 
      'background_medium' => 'http://mydomain.com.au/wp-content/uploads/facade-1366x807.jpg', 
      'background_small' => 'http://mydomain.com.au/wp-content/uploads/facade-1024x605.jpg '
   ),
   array(
      'background_large' => 'http://mydomain.com.au/wp-content/uploads/facade-trees.jpg', 
      'background_medium' => 'http://mydomain.com.au/wp-content/uploads/facade-trees-1366x818.jpg', 
      'background_small' => 'http://mydomain.com.au/wp-content/uploads/facade-trees-1024x613.jpg '
   )    
 );

You almost had it.

function ajax_get_latest_posts(){   
   $attachments = get_children(array('post_parent' => $post->ID,
                    'post_status' => 'inherit',
                    'post_type' => 'attachment',
                    'post_mime_type' => 'image',
                    'order' => 'ASC',
                    'orderby' => 'menu_order ID'));

   $allimagesizes = array();
   foreach($attachments as $att_id => $attachment) {
      $large_bg_url = wp_get_attachment_image_src($attachment->ID, 'background-large');
      $medium_bg_url = wp_get_attachment_image_src($attachment->ID, 'background-medium');
      $small_bg_url = wp_get_attachment_image_src($attachment->ID, 'background-small');
      $imagesizes = array('background_large' => $large_bg_url[0], 'background_medium' => $medium_bg_url[0], 'background_small' => $small_bg_url[0]);
      $allimagesizes[] = $imagesizes;
   }
   return $allimagesizes;
}

Should work.

First off we defined the array before the foreach.

Remove the concatenation operator from the imagesizes assignment.

Next we are pushing the array created in the loop into the $allimagessizes array inside the loop.

Use this:

$allimagesizes[] = $imagesizes;

Putting [] after the array name means to add a new element to the end of the array.

Also, in the assignment to $imagesizes, you should use =, not .=. The latter is for appending to a string.