, // then try uncommenting the following line: // $multi_curl->setHeader('Content-Type', 'multipart/form-data'); $multi_curl->addPost('https://httpbin.org/post', [ 'image' => new CURLFile('the-lorax.jpg'), ]); $multi_curl->addPost('https://httpbin.org/post', [ 'image' => new CURLFile('swomee-swans.jpg'), ]); $multi_curl->addPost('https://httpbin.org/post', [ 'image' => new CURLFile('truffula-trees.jpg'), ]); $multi_curl->start();