mixed File_Passwd_Authdigest::addUser ( 
    string $user
     , string $realm
     , string $pass
   )
Add an user to the AuthDigestFile.
$user and $realm must start with an alphabetical charachter and must NOT contain any other characters than alphanumerics, the underline and dash.
$user
     the user to add
$realm
     the realm the user should be in
$pass
     the plaintext password
Returns TRUE on success, PEAR_Error on failure.
| Error Code | Summary | 
|---|---|
| FILE_PASSWD_E_EXISTS_ALREADY | user already exists in the supplied realm | 
| FILE_PASSWD_E_INVLAID_CHARS | user or realm contains illegal characters | 
This function can not be called statically.