我创建了一个名为“pdf”的自定义帖子类型。我有一个自定义的metabox，用户可以通过wordpress内置媒体上传器上传pdf文件。我需要在这个上传器中限制允许的文件（pdf）。我已经知道如何限制允许的文件：How to set file type in wp_handle_upload?但是上面的链接干扰了所有的上传。有什么提示吗？

谢谢

编辑：我发现了如何在plupload中限制文件类型，所以我解决了一半问题：

 add_filter( \'plupload_init\', \'my_plupload_init\', 0, 1 );

 function my_plupload_init( $plupload_init ) {
 $plupload_init[\'filters\'] = array( array(\'title\' => __( \'Allowed Files\' ), \'extensions\' => \'pdf\') );
 return $plupload_init;
}

编辑#2：使用wp\\u handle\\u upload\\u prefilter过滤器不起作用：这是在将图像上载到新帖子后$\\u请求对象中可用的内容：

    array
  \'type\' => string \'image\' (length=5)
  \'tab\' => string \'type\' (length=4)
  \'post_id\' => string \'0\' (length=1)
  \'_wpnonce\' => string \'375c5f46f2\' (length=10)
  \'_wp_http_referer\' => string \'/wp-admin/media-upload.php?post_id=\' (length=37)
  \'html-upload\' => string \'Carica media\' (length=12)

没有关于我的自定义帖子类型的信息。id为0，因为帖子尚未保存。

编辑#3：

感谢@TheDeadMusic answer，我在javascript中添加了一行代码。这是我实际使用的非常有效的js代码：

jQuery(document).ready(function($){
// #btn_upload is my custom button
$(\'#btn_upload\').click(function(event){
    event.preventDefault();
    var backup = window.send_to_editor;
    var src=\'\'; 
//post_id is always set so I can pass it safely to tickbox
    var post_id=$(\'#post_ID\').val(); 
var target=$(\'#pdf_url\');
    window.send_to_editor = function(html) 
     {
//I have to get the link to "original file" from html returned by tickbox
        link = $(\'a\',html).attr(\'href\');
         $(target).val(link);
         tb_remove();
         window.send_to_editor=backup; //reset default action
    }
    //show the uploader
     tb_show(\'\', \'media-upload.php?post_id=\'+post_id+\'&TB_iframe=true\');

}); 

});

function wpse_59621_mimes_filter( $mimes ) {
    return array( \'pdf\' => \'application/pdf\' );
}

function wpse_59621_delay_mimes_filter( $value ) {
    if ( isset( $_REQUEST[\'post_id\'] ) && get_post_type( $_REQUEST[\'post_id\'] ) === \'my_post_type\' )
        add_filter( \'upload_mimes\', \'wpse_59621_mimes_filter\' );
    else
        remove_filter( \'upload_mimes\', \'wpse_59621_mimes_filter\' );

    return $value;
}

add_filter( \'wp_handle_upload_prefilter\', \'wpse_59621_delay_mimes_filter\' );