Ubuntu上的LAMP创建写保护文件

I have set up a Ubuntu LAMP server, and everything is working fine, however, I have a PHP script that allows the user to upload files to a directory within the www directory. The files saved via PHP are chmod 644.

How can I change the setting so that the files saved on the server are chmod 755 by default?

1. Educate yourself as to what a umask is.
2. Use the umask() function.