使用时wp_handle_sideload 正如@xvilo在评论中指出的那样，它并没有创建wordpress在媒体库中显示图像所需的元数据。因为我看不到wp_handle_sideload 函数正在将数据写入数据库，我不明白为什么文件会显示在媒体库中。因此，在你的方法中，你错过了wp_insert_attachment （正如你自己所说）和wp_generate_attachment_metadata.

$temp_file = download_url( $url, 5 );
$file = array(
     \'name\'     => basename($url),
     \'type\'     => \'image/jpg\',
     \'tmp_name\' => $temp_file,
     \'error\'    => 0,
     \'size\'     => filesize($temp_file),
);
$overrides = array(
     \'test_form\' => false,
     \'test_size\' => true,
);
// Move the temporary file into the uploads directory
$results = wp_handle_sideload( $file, $overrides );

// Write attachment to db
$attachment = [
    \'post_title\' => basename($results[\'file\']),
    \'post_content\' => \'\',
    \'post_status\' => \'inherit\',
    \'post_mime_type\' => $results[\'type\'],
];
$attachment_id = wp_insert_attachment( $attachment, $results[\'file\'] )

// Generate the attachment\'s meta data
wp_generate_attachment_metadata( $attachment_id, $results[\'file\'] );

$attachment_id = media_handle_sideload( $file_array, 0 );

set_post_thumbnail( $post, $attachment_id );