i am new to chmod and would like to know what are value like 644/755/777 etc are. i searched google and most gave me info on linux ones like -wx etc. how do i convert whose to numeric ones PHP uses?

http://www.ss64.com/bash/chmod.html

uid0's link is excellent (especially the little calculator tool) but here are some Wiki links to go with it:
http://en.wikipedia.org/wiki/Chmod
http://en.wikipedia.org/wiki/File_system_permissions

fun PHP, for some reason they dont always work correctly, for me at least.
give this a quick read:
http://us3.php.net/chmod

and from above, http://www.ss64.com/bash/chmod.html, this has a calculator in it for the values