If you're set on PHP jobs in Kassel, there aren't very many at present: we count 2. Maybe, you could try slightly farther afield. Two main themes in this field include C++ jobs and Front End Development jobs. Opportunities that require MySQL, WordPress, or Web Development are often cited in job offers in this area.
Unfortunately for those looking for an internship in the area of PHP, employers in this area are mainly hiring trained job seekers. What kind of job are you looking for? Sign up to Jobspotting to find a highly relevant opportunity!