OK..I finally got it to work with the DPZ library.
For future reference anybody facing the same problem as I had:
I managed to create an album using DPZFlickr by changing the method in auth.php to flickr.photosets.create....which indicated that the library correctly generates an access token with write permission..
However, the upload example kept giving me the "Invalid signature" error....
I checked the code. Flickr.php correctly unsets the photo parameter before signing the request then adds it back and submits the request which is exactly as indicated in: www.flickr.com/services/api/upload.api.html
I found a discussion in https://www.flickr.com/groups/51035612836@N01/discuss/72157650261711318/ that cleared out that the error was not actually a signature problem, but rather the 'photo' parameter that is being sent is the problem. It's just that Flickr doesn't know what to do with the photo parameter so it sends the signature error.
So what' wrong with the photo parameter?
Flickr API requires that the image has to be sent in binary form...The DBZ library, Flickr.php script line 677, does the hard work for us using the cURL function in php (http://au.php.net/manual/en/function.curl-setopt.php).
It sends the $parameters (which includes the uploaded photo) to the post field of the http request which should do the upload in binary format for us.
However, a brilliant comment I found in CURL PHP send image
states that:
"CURLOPT_SAFE_UPLOAD defaulted to true in 5.6.0... so you will need to add curl_setopt($ch, CURLOPT_SAFE_UPLOAD, false); before setting CURLOPT_POSTFIELDS"
Checking the manual: http://au.php.net/manual/en/function.curl-setopt.php
it says:
"Added in PHP 5.5.0 with FALSE as the default value. PHP 5.6.0 changes the default value to TRUE."
So if your php version is 5.5.0 the library will work just fine whilst if using version PHP 5.6.0 you need to add a line before 677 in Flickr.php to change the CURLOPT_SAFE_UPLOAD to false (that's why the library works with some and others not).
To solve the issue...Just add this line before line 677 in Flickr.php:
curl_setopt($curl, CURLOPT_SAFE_UPLOAD, false);
That's it. (-: