Core Security Technologies today announced the release of CORE GRASP, which is a patch against the PHP 5.2.3 code tree that adds a tainted mode to PHP to protect 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.
To add such a tainted mode to PHP has been discussed several times in the past. It was rejected for several reasons like the obvious huge speed impact and the danger of false positives and a false sense of security. And indeed the way CORE GRASP is implemented it looks like a huge memory and speed overhead that should be tested. In addition to that their query parser will for example wrongly detect quotes escaped by doubling as injection attack.
Aside from this there are several other possible problems in the code like a remote one byte stack overflow (that seems harmless due to memory alignment), wrong handling of the _SERVER superglobal in case of JIT and it also seems that control characters like linebreaks can be injected into the logfiles. Further analysis and a deeper look into the code is needed.
However it has to be taken into account that this is the very first public version of CORE GRASP, so maybe all these problems are gone soon and support for further database engines is added.