Stefan Esser points out a new patch today -
CORE GRASP - from the
Core Security Technologies group that provides taint support surrounding the mysql_query function.
Their implementation adds a tainted or not flag for every byte so that it is possible on invocation of mysql_query() to determine any kind of injection.
Unfortunately,
Stefan also mentions two big issues it might have from the get-go: the overhead for the memory needed can slow things down and an incorrect parsing in their query handler could lead to injection attacks.
Stefan Esser's Blog: CORE GRASP - PHP Tainted Mode - Read More... 
