PHP HTTP POST Request - php

Question

I need to send an XML string via HTTP POST to another server using the settings below...
POST /xmlreceive.asmx/CaseApplicationZipped HTTP/1.1
Host: www.dummyurl.co.uk
Content-Type: application/x-www-form-urlencoded
Content-Length: length
XMLApplication=XMLstring&byArray=base64string
I'm guessing I need to set this up via cURL or maybe fsockopen.
I've tried the following but not having any luck at getting it to work.
$url = "http://www.dummyurl.co.uk/XMLReceive.asmx/CaseApplicationZipped";
$headers = array(
"Content-Type: application/x-www-form-urlencoded"//,
);
$post = http_build_query(array('XMLApplication' => $XML, 'byArray' => $base64));
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, $post);
curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$response = curl_exec($ch);
curl_close($ch);
echo "response: ".$response;
The remote server gives the following response...
"Object reference not set to an instance of an object."

Answer 1

Not enough rep yet to comment, so I'll post this as an answer.
PHP's cURL automatically send the Host (from $url) and the Content-Length headers, so you don't need to specify those manually.
A handy function exists for building the $post string: http_build_query. It'll handle properly encoding your POST body. It would look something like
$post = http_build_query(array('XMLApplication' => $XML, 'byArray' => $base64));
If you want to log out the headers you received, check the curl_getopt function.
As for the error you received, it seems like you're passing the remote site things it doesn't expect. I can't speak for what you're passing or what the site's expecting, but Input string was not in a correct format seems to imply that your $XML is not formatted correctly, or is being passed as an incorrect parameter.