In his latest post Simon Champion recounts some of the issues he had when upgrading to PHP 5.4, what's usually a smooth transition from PHP 5.3. His specific problem came in a difference between the previous mysql_query call and the more-correct PDO usage.

Our office is in the thoes of a large-scale upgrade of the servers in our data center. The new version of Debian (version 7, or "Wheezy") has been officially released, having been in beta for the last few millenia, and our Ops team are slowly installing it across all our servers. This is great news, as it means we get to upgrade to PHP 5.4. Woohoo! New shininess. [...] We were ready. The upgrade should have been a breeze. But it wasn't.

He talks about his process of digging through the code trying to figure out why a call to import a CSV file into MySQL was failing. Their Data Importer component started failing with an error from MySQL about the "LOAD INFILE" not being allowed for use. He shares a "work around" that's not ideal (using exec) that manually imports the file into the database. He does point out that it could be something Debian-specific as they don't upgrade the version, just apply security patches retroactively.

We're making an effort to stick to modern PHP coding standards, so we're using PDO throughout, which makes is all the more galling. [...] Given that we do have a work-around now and everything is back up and running, I'm going to have to let this one drop; I don't have the time to try chasing it any more. But I hope this blog post will prove useful to anyone else having the same issue.