Multipart form file upload POST PHP cURL

Question

I am wanting to send a file via http POST using PHP and cURL.

The form POST was working ok with basic fields besides the file being posted with \'application/json\'.

Answer 1

This all gets very confusing and "contradictory" very quickly! Because cUrl is quite flexible and powerful, little differences in usage context have a massive impact and can lead to DAYS of non-existent bug chasing.

Secondly, the URL/Endpoint you are posting to can also have it own "implementation" and expectations. This understanding it complicated when experience is only with GET requests AND the assumption/expectation is based of PHP Super Easy $_REQUEST

In the case above, simplifying: This is a live working example, but the postfields ($post) has been reduced from the 50 odd in use to a few for example. This will post as multipart form data.

Here important options are the options to use CURLOPT_POST and CURLOPT_POSTFIELDS and NOT CURLOPT_CUSTOMREQUEST. Doing so will require you to take care of required headers and in particular, content size header, etc.

// Post "field" array. Notice its 1 Dimensional. Else, this should rather accept JSON. simply decode array to json and proceed). Depends what server is expecting - Form data, Form + files, json or maybe just a RAW request body.
$post = array(  
            'RsmMaster1_TSM' => $tsm,
            '__EVENTTARGET' => '__Page',
            '__EVENTARGUMENT' => 'ExcelExport',
            '__VIEWSTATE'  => $viewstate,
            '__VIEWSTATEGENERATOR'  => $viewstategenerator,
            '__EVENTVALIDATION'  => $eventvalidation
 );

// Optional, Required in THIS case because, well gosh darn who knows, as the receiving server admin?
$headers = array(   
                'Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8',
                'Accept-Language: en-ZA,en-GB;q=0.8,en-US;q=0.5,en;q=0.3',
                'Referer: https://example.com/Main.aspx'  
            );

// cUrl it into the goal!
$ch = curl_init();

curl_setopt($ch, CURLOPT_URL, 'https://example.com/Main.aspx');
curl_setopt($ch, CURLOPT_POST, TRUE);
curl_setopt($ch, CURLOPT_POSTFIELDS, $post);                                                                  
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true); 
curl_setopt($ch, CURLOPT_USERAGENT, "Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.7.12) Gecko/20050915 Firefox/1.0.7");
curl_setopt($ch, CURLOPT_ENCODING, 'gzip,deflate');                                                                   
curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);    
curl_setopt($ch, CURLOPT_HEADER, 0);
// curl_setopt($ch, CURLOPT_COOKIEFILE, $cookie); // Session maintain!
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
curl_setopt($ch, CURLOPT_FAILONERROR,    TRUE   );
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, FALSE  );
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, FALSE  );

$content = curl_exec($ch);
curl_close($ch);