CGI::Session::Driver - phpMan

NAME
    CGI::Session::Driver - CGI::Session driver specifications

SYNOPSIS
        require CGI::Session::Driver;
        @ISA = qw( CGI::Session::Driver );

DESCRIPTION
    CGI::Session::Driver is a base class for all CGI::Session's native
    drivers. It also documents driver specifications for those willing to
    write drivers for different databases not currently supported by
    CGI::Session.

WHAT IS A DRIVER
    Driver is a piece of code that helps CGI::Session library to talk to
    specific database engines, or storage mechanisms. To be more precise,
    driver is a .pm file that inherits from CGI::Session::Driver and defines
    retrieve(), store() and remove() methods.

  BLUEPRINT
    The best way of learning the specs is to look at a blueprint of a
    driver:

        package CGI::Session::Driver::your_driver_name;
        use strict;
        use base qw( CGI::Session::Driver CGI::Session::ErrorHandler );

        sub init {
            my ($self) = @_;
            # optional
        }

        sub DESTROY {
            my ($self) = @_;
            # optional
        }

        sub store {
            my ($self, $sid, $datastr) = @_;
            # Store $datastr, which is an already serialized string of data.
        }

        sub retrieve {
            my ($self, $sid) = @_;
            # Return $datastr, which was previously stored using above store() method.
            # Return $datastr if $sid was found. Return 0 or "" if $sid doesn't exist
            }

        sub remove {
            my ($self, $sid) = @_;
            # Remove storage associated with $sid. Return any true value indicating success,
            # or undef on failure.
        }

        sub traverse {
            my ($self, $coderef) = @_;
            # execute $coderef for each session id passing session id as the first and the only
            # argument
        }

        1;

    All the attributes passed as the second argument to CGI::Session's new()
    or load() methods will automatically be made driver's object attributes.
    For example, if session object was initialized as following:

        $s = CGI::Session->new("driver:your_driver_name", undef, {Directory=>'/tmp/sessions'});

    You can access value of 'Directory' from within your driver like so:

        sub store {
            my ($self, $sid, $datastr) = @_;
            my $dir = $self->{Directory};   # <-- in this example will be '/tmp/sessions'
        }

    Optionally, you can define "init()" method within your driver to do
    driver specific global initialization. "init()" method will be invoked
    only once during the lifecycle of your driver, which is the same as the
    lifecycle of a session object.

    For examples of "init()" look into the source code of native
    CGI::Session drivers.

METHODS
    This section lists and describes all driver methods. All the driver
    methods will receive driver object ($self) as the first argument.
    Methods that pertain to an individual session (such as "retrieve()",
    "store()" and "remove()") will also receive session id ($sid) as the
    second argument.

    Following list describes every driver method, including its argument
    list and what step of session's life they will be invoked. Understanding
    this may help driver authors.

    retrieve($self, $sid)
        Called whenever a specific session is requested either via
        "CGI::Session->new()" or "CGI::Session->load()" syntax. Method
        should try to retrieve data associated with $sid and return it. In
        case no data could be retrieved for $sid 0 (zero) or "" should be
        returned. undef must be returned only to signal error. Error message
        should be set via set_error(), which can be inherited from
        CGI::Session::ErrorHandler.

        Tip: set_error() always returns undef. Use it for your advantage.

    store($self, $sid, $datastr)
        Called whenever modified session data is to be stored back to disk.
        This happens whenever CGI::Session->flush() is called on modified
        session. Since CGI::Session->DESTROY() calls flush(), store() gets
        requested each time session object is to be terminated.

        " store() " is called both to store new sessions and to update
        already stored sessions. It's driver author's job to figure out
        which operation needs to be performed.

        $datastr, which is passed as the third argument to represents
        already serialized session data that needs to be saved.

        store() can return any true value indicating success or undef on
        failure. Error message should be passed to set_error()

    remove($self, $sid)
        Called whenever session data is to be deleted, which is when
        CGI::Session->delete() is called. Should return any true value
        indicating success, undef on failure. Error message should be logged
        in set_error().

    traverse($self, \&coderef)
        Called only from within CGI::Session->find(). Job of traverse() is
        to call \&coderef for every single session stored in disk passing
        session's id as the first and only argument: "$coderef->( $sid )"

    init($self)
        Optional. Called whenever driver object is to be initialized, which
        happens only once during the lifecycle of CGI::Session object. Here
        you can do driver-wide initialization, such as to open connection to
        a database server.

    DESTROY($self)
        Optional. Perl automatically calls this method on objects just
        before they are to be terminated. This gives your driver chance to
        close any database connections or close any open file handles.

  NOTES
    *   All driver .pm files must be lowercase!

    *   DBI-related drivers are better off using CGI::Session::Driver::DBI
        as base, but don't have to.

BACKWARDS COMPATIBILITY
    Version 4.0 of CGI::Session's driver specification is NOT backward
    compatible with the previous specification. If you already have a driver
    developed to work with the previous version you're highly encouraged to
    upgrade your driver code to make it compatible with the current version.
    Fortunately, current driver specs are a lot easier to adapt to.

    For support information see CGI::Session

LICENSING
    For support and licensing see CGI::Session.