PHP cURL将文件设置为POST表单输入类型文件

I have a page on a different server with a <form> and I use cURL to set the data automatically. However in this form there is a file input <input name='file' type='file'> and now I am aware of the fact that the file input behaves differently from the others.

//This is my code till now.
$ch = curl_init();
//page is password protected I am not sure if this works but I hope it does.
curl_setopt($ch, CURLOPT_URL, "http://user:pass@mydomain.com/system_backup.php");
curl_setopt($ch, CURLOPT_POST, 1);
//set a file as post variable this doesn't work
curl_setopt($ch, CURLOPT_POSTFIELDS, "file=".$file."&var1=".$var1."&var2=".$var2);
$result = curl_exec($ch);
curl_close($ch);

So my question is how do I set a file as a postfield with cURL.

found the solution myself

$postParams['file'] = '@'.realpath("URLTOFILE.txt"); //for type = file
$postParams['var1'] = urlencode("var1"); //type = text, submit pretty much everything.

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, "http://user:pass@mydomain.com/system_backup.php");
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, $postParams);

Look at this guide, you need to prefix the file full path with '@'

You can put the params in an array as $postFields = array('file'=>$file,'var1'=>$var1,'var2'=>$var2);

and then use curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query($postFields));

Hopefully should work.