what are the different ways to use the variable in many functions within a module? I want to access a variable changed in one function in another. I tried this with Session and global variables. I need the variable to be persisted across multiple page requests. are there any other ways to do this?
variable_set


  sets a persistent variable.
  
  Case-sensitivity of the variable_* functions depends on the database
  collation used. To avoid problems, always use lower case for
  persistent variable names.


variable_get


  Returns a persistent variable.
  
  Case-sensitivity of the variable_* functions depends on the database
  collation used. To avoid problems, always use lower case for
  persistent variable names.


variable_del


  Unsets a persistent variable.
  
  Case-sensitivity of the variable_* functions depends on the database
  collation used. To avoid problems, always use lower case for
  persistent variable names.