While logging in with a WebID, the following warning appear:

Strict warning: Accessing static property FoafParser::$graphite as non static in FoafParser->getImage() (line 52 of sites/all/modules/webid/webidauth.parser.inc).

Strict warning: Non-static method Graphite::asString() should not be called statically, assuming $this from incompatible context in Graphite_Resource->__toString() (line 1171 of sites/all/libraries/Graphite/Graphite.php).

These warnings do not appear on PHP 5.3