I solved my own problem. There were two main problems with the above code:
1) The $fields
array was incorrectly formatted for the input_files[]
. It needed a @/
and mime-type declaration (see code below)
2) The curl_exec()
output (the actual newly created file contents) needed to be returned and not just true/false
which is this function's default behavior. This is accomplished by setting the curl option curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
(see code below).
Full working example
//set POST variables
$url = 'http://c.docverter.com/convert';
$fields = array('from' => 'markdown',
'to' => 'pdf',
'input_files[]' => "@/".realpath('markdown.md').";type=text/x-markdown; charset=UTF-8"
);
//open connection
$ch = curl_init();
//set options
curl_setopt($ch, CURLOPT_HTTPHEADER, array("Content-type: multipart/form-data"));
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_POSTFIELDS, $fields);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true); //needed so that the $result=curl_exec() output is the file and isn't just true/false
//execute post
$result = curl_exec($ch);
//close connection
curl_close($ch);
//write to file
$fp = fopen('uploads/result.pdf', 'w'); //make sure the directory markdown.md is in and the result.pdf will go to has proper permissions
fwrite($fp, $result);
fclose($fp);