Swap36

I have use apache server with PHP installed on it,i created one directory through php coding it get created but it has permission ( drwxr-sr-x 3 www-data www-data 4096 Feb 26 04:54 Merchantid_30) my other directories has ubuntu:ubuntu permission, I want to write on my directory but www-data wont allow me to write on it,giving 777 permission through chmod is risky, can i create directory through php but its default permission is set to be ubuntu:ubuntu instead of www-data ? what changes i need to do in coding?