Strangely enough the server can't resize images any more because it doesn't have enough write permissions. When I check the permissions of the directory I want to write my resized images to I see:
username staff
After excecuting echo exec('whoami'); and checking the httpd.conf I saw the user and group for the server was daemon:daemon (this seems to be the default for Zend Server CE on an OSX installation). What should I do so I have enough permissions again. Should I chown my directory to daemon:daemon (what isn't working). Should I change the user of the server or something else?