Construct a PHP POST request with binary data - php

Question

I'm trying to construct a PHP POST request that includes some binary data, following on from a previous StackOverflow question. The data is being submitted to this API call: http://www.cyclestreets.net/api/#addphoto
This is my PHP code:
$file = $_FILES['mediaupload'];
$file_field="#$file[tmp_name]";
$fields = array(
'mediaupload'=>$file_field,
'username'=>urlencode($_POST["username"]),
'password'=>urlencode($_POST["password"]),
'latitude'=>urlencode($_POST["latitude"]),
'longitude'=>urlencode($_POST["longitude"]),
'datetime'=>urlencode($_POST["datetime"]),
'category'=>urlencode($_POST["category"]),
'metacategory'=>urlencode($_POST["metacategory"]),
'caption'=>urlencode($_POST["description"])
);
$fields_string = http_build_query($fields);
echo 'FIELDS STRING: ' . $fields_string;
$url = 'https://www.cyclestreets.net/api/addphoto.json?key=$key';
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL,$url);
curl_setopt($ch,CURLOPT_POST,count($fields));
curl_setopt($ch,CURLOPT_POSTFIELDS,$fields_string);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
$response = curl_exec ($ch);
This is what my PHP file outputs:
FIELDS STRING: mediaupload=%40%2Fprivate%2Fvar%2Ftmp%2FphpHjfkRP&username=testing&password=testing&latitude=auto&longitude=auto&datetime=auto&category=cycleparking&metacategory=good&caption=
API RESPONSE: {"request":{"datetime":"1309886656"},"error":{"code":"unknown","message":"The photo was received successfully, but an error occurred while processing it."},"result":{}}
I believe this means that everything else about the request is OK, apart from the format of the binary data. Can anyone tell me what I am doing wrong?

Answer 1

CURL can accept a raw array of key=>value pairs for POST fields. There's no need to do all that urlencode() and http_build_query() stuff. Most likely the # in the array is being mangled into %40, so CURL doesn't see it as a file upload attempt.
$fields = array(
'mediaupload'=>$file_field,
'username'=> $_POST["username"),
etc...
curl_setopt($ch,CURLOPT_POSTFIELDS,$fields);

Answer 2

The http_build_query function generates a URL encoded query string which means that the "#file.ext" is URL encoded in the output as a string and cURL doesn't know that you're trying to upload a file.
My advice would be not to include the file to upload in the http_build_query call and included manually in the CURLOPT_POSTFIELDS.
$file = $_FILES['mediaupload'];
$file_field="#$file[tmp_name]";
$fields = array(
'username'=>urlencode($_POST["username"]),
'password'=>urlencode($_POST["password"]),
'latitude'=>urlencode($_POST["latitude"]),
'longitude'=>urlencode($_POST["longitude"]),
'datetime'=>urlencode($_POST["datetime"]),
'category'=>urlencode($_POST["category"]),
'metacategory'=>urlencode($_POST["metacategory"]),
'caption'=>urlencode($_POST["description"])
);
$fields_string = http_build_query($fields);
echo 'FIELDS STRING: ' . $fields_string;
$url = 'https://www.cyclestreets.net/api/addphoto.json?key=$key';
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL,$url);
curl_setopt($ch,CURLOPT_POST, 1);
curl_setopt($ch,CURLOPT_POSTFIELDS, 'mediaupload=' . $file_field . '&' . $fields_string);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
$response = curl_exec ($ch);