PEAR::Auth uses a number of so called storage containers to store the login data. The following passages describe all of them. If the containers that come with the package don't fit your needs, it is easy to create custom ones, also.
Storage container using a PHP Array.
Storage container using PEAR DB.
A simplified version of the DB container that only provides user authentication. No user management functions are provided.
Storage container using PEAR File_Passwd.
Storage container for use against IMAP servers.
Storage container for use against Kerberos V servers.
Storage container for use against LDAP servers.
Storage container using PEAR MDB.
Storage container using PEAR MDB2.
Storage container for use against the PEAR website.
Storage container for use against a POP3 server.
Storage container for use against a RADIUS server.
Storage container for use against a SAP server.
Storage container using PEAR File_SMBPasswd.
Storage container for use against a SOAP service using PEAR SOAP as the client.
Storage container for use against a SOAP service using PHP5 SOAP as the client.
Storage container using vpopmail.
Instructions on creating a custom storage container.