Set label on folder

semanage fcontext -a -t samba_share_t <complete-path-to-folder>

Set label also on subfolder and files

semanage fcontext -a -t samba_share_t "<complete-path-to-folder>(/.*)?"

Quotes are required!

Restore label

Also used to apply labels to sub directories. 

restorecon -Rv <complete-path-to-folder>

Allow PHP connection to external DB server

setsebool -P httpd_can_network_connect 1
setsebool -P httpd_can_network_connect_db 1