How to detect default avatar on the link like this: https://graph.facebook.com/\'.$id.\'/picture?type=large?
Is it the only way to get avatars (male/female) fr
There isn't an API you can call to tell if they are using the default photo or not. Instead of downloading the whole image and checking the MD5, you could issue an HTTP HEAD request to that profile URL and look at the Location header and see if the URL is one of the known default profile images:
Male: https://fbcdn-profile-a.akamaihd.net/static-ak/rsrc.php/v2/yL/r/HsTZSDw4avx.gif

Female (Darth Vader):https://fbcdn-profile-a.akamaihd.net/static-ak/rsrc.php/v2/yp/r/yDnr5YfbJCH.gif

These URL's could change I suppose, and so could the default photos, but I haven't seen either case happen that I can remember.