PHP CURL use proxy to POST - php

Question

I'm trying to create a script that posts to an URL, using a list of proxies. The script seems to work fine without setting a proxy (CURLOPT_PROXY to null), but with a proxy set it does not seem to work. Does anybody know what I'm doing wrong here? The error I'm getting when posting with a proxy is:
ERROR
The requested URL could not be retrieved
Invalid Request error was encountered while trying to process the request:
POST /###/ HTTP/1.1
Host: ###
Accept: */*
Proxy-Connection: Keep-Alive
Content-Length: 368
Expect: 100-continue
Content-Type: multipart/form-data; boundary=----------------------------9b24e849cac0
Some possible problems are:
Missing or unknown request method.
Missing URL.
Missing HTTP Identifier (HTTP/1.0).
Request is too large.
Content-Length missing for POST or PUT requests.
Illegal character in hostname; underscores are not allowed.
And my code is:
$url = 'urltopost';
$proxy = 'proxy:port';
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL,$url);
curl_setopt($ch, CURLOPT_PROXY, $proxy);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_HEADER, 1);
curl_setopt($ch, CURLOPT_POST, true);
$data = array(
'postname1' => 'value1',
'postname2' => 'value2'
);
curl_setopt($ch, CURLOPT_POSTFIELDS, $data);
$curl_scraped_page = curl_exec($ch);
curl_close($ch);
echo $curl_scraped_page;

Answer 1

You are missing the PROXYPORT option... You can't use the proxy:port notation
curl_setopt($ch, CURLOPT_PROXY, "YOUR PROXY HOST");
curl_setopt($ch, CURLOPT_PROXYPORT, "YOUR PROXY PORT");