我需要通过media box检查要上载的图像的分辨率，然后将其上载到自定义目录。

作为起点，我使用了How Can I Organize the Uploads Folder by Slug (or ID, or FileType, or Author)?

其中一部分是这样的：

function wpse_25894_custom_upload_dir($path)
{   

    $use_default_dir = ( isset($_REQUEST[\'post_id\'] ) && $_REQUEST[\'post_id\'] == 0 ) ? true : false; 
    if( !empty( $path[\'error\'] ) || $use_default_dir )
        return $path; //error or uploading not from a post/page/cpt 

    //THIS LINE PRODUCE ERROR. HERE I NEED TO GET WIDTH AND HEIGHT OF IMAGE I WANT TO UPLOAD
    list($width, $height) = getimagesize($path.\'/\'.$_POST[\'name\']); 
    $customdir = \'/\'.$width.\'x\'.$height; //uplaod folder will be for example \'640x480\'

    $path[\'path\']    = str_replace($path[\'subdir\'], \'\', $path[\'path\']); //remove default subdir (year/month)
    $path[\'url\']     = str_replace($path[\'subdir\'], \'\', $path[\'url\']);      
    $path[\'subdir\']  = $customdir;
    $path[\'path\']   .= $customdir; 
    $path[\'url\']    .= $customdir;  

    return $path;
}