Ask HN: I am forced to write awful code What do I do?

So the story is: I got a new job as a PHP web developer at a rather respectable digital studio in UK. I was very enthusiastic about this one but now, after 3 months, I am building and maintaining websites using a CMS built in 2005. The code is far from being up to standards, MVC being something that I can only dream about.

To have an idea about the code I am going to tell you that we have a PHP class called dbConfig which stores database credentials. This class is then extended by a DB class which has query functions and other functions that deal with data retrieval from the db. This class (DB) is then extended by a class called front-end which has some functions that generate forms and escape inputs. this class (front-end) is then extended by a Cart class that deals with user logic and creates a sort of a fully functioning shopping cart (amazing i know!).

All this badly implemented inheritance is topped up by the fact that global variables are used throughout the site/app. It is an awful procedural codebase (at one point it even uses magic quotes). Everything single job becomes a bodge job. If I have to change something it then creates an error in a totally different part of the website.

I have suggested that we move towards a MVC framework or something that will help with this horrible dependencies and will probably decouple most of the things, so that code maintenance would be easier. Sadly, it seems that the company is more interested in spewing up websites and cashing in the money (from some rather big international clients) than in creating better quality software.

Now that you know my situation.. here comes the question: What should I do? How can I speed up the transition to a development process that is up to the industry standards? (did I tell you that we still deploy apps with FTP and have htaccess authentication for the web administration area??) I am sure that there are some developers among you that have been in my situation at one point in their career... so what did you do? How can I say this to my boss? I don't want to be responsible for crappy websites that pollute the internet, I don't want to keep on bodging code.... but at the same time, I don't really want to change my workplace (it's well paid, close to home, etc. etc.)

Thank you all, and... I'm sorry for the rubbish I upload every day!