I have unzipped the latest version of cakephp into /home/username/public_html/cakephp

I have baked an app:

cd /home/username/public_html/cakephp/cake/console

./cake bake -app /home/username/public_html/mapdb-dev

And then I hit the errors of access denied to the mapdb-dev/tmp directory even though it's full access (777) for everyone

The problem is the SeLinux context

cd /home/username/public_html/mapdb-dev

ls -Z tmp/
drwxrwxrwx. username usergroup unconfined_u:object_r:httpd_user_content_t:s0 cache
drwxrwxrwx. username usergroup unconfined_u:object_r:httpd_user_content_t:s0 logs
drwxrwxrwx. username usergroup unconfined_u:object_r:httpd_user_content_t:s0 sessions
drwxrwxrwx. username usergroup unconfined_u:object_r:httpd_user_content_t:s0 tests

You need to change the seLinux context:
chcon -Rv --type=httpd_user_content_rw_t tmp/

changing security context of `tmp/logs'
changing security context of `tmp/cache/models'
changing security context of `tmp/cache/views'
changing security context of `tmp/cache/persistent'
changing security context of `tmp/cache'
changing security context of `tmp/sessions'
changing security context of `tmp/tests'
changing security context of `tmp/

# to get things going very quickly with cakephp
# do a bake  all in this order
./cake bake -app /home/username/public_html/mapdb-dev/ model all
./cake bake -app /home/username/public_html/mapdb-dev/ controller all
./cake bake -app /home/username/public_html/mapdb-dev/ view all