找到答案了，我需要 json_encode 属性数组，然后使用 new \CURLFile（）函数创建文件句柄，它不适用于 realpath（）

Found the answer, i needed to json_encode the attributes array and then use new \CURLFile() function to create a file handle, it did NOT work with realpath()

$attributes = array('name'=>$fileName,'parent'=>array('id'=>$folderId));
$file = new \CURLFile($filePath);
$fields = array('attributes' => json_encode($attributes), 'file' => $file);
$headers = array("Authorization: Bearer ".$accessToken);

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $uploadUrl);
curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, $fields);

$result = curl_exec($ch);