adding image to an array and submit it via curl

I've trouble sending image from url to remote host using curl. Everything else works.

// assemble full image path

foreach ( $respArr[ 'imgs' ] as $k => $v) {

    $car[ 'photos' ][ $k ] = file_get_contents( 'http://' . $v[ 'ipt' ] . '/im/im-' . $v[ 'ikey' ] ); // full url?

}

The issue is that I don't understand how browser sends images, it creates array, than this array content is invisible to me when I try to dump the $_POST.

Any clarification in this area is welcome :)