php - preg_match for select string like #__james_name -

i need regular expression select text #__james_name in php tried :

(^#__[a-z]*)*   

but did not succeed.
please

update
tried :

\#__([a-z]*)_([a-z]*) 

how using in preg_match ?

preg_match('/(^#__[a-z_]*)/', '#__james_name', $matches);