Например, так:
sess1.php:

PHP код:
<?php
session_start ();
session_register ( "myvar" );
echo ( "<A HREF=\"sess2.php\">sess2</A>" );
echo ( $myvar . "<BR>" );
?>
sess2.php:

PHP код:
<?php
session_start ();
session_register ( "myvar" );
$HTTP_SESSION_VARS["myvar"] = $myvar;
echo ( $myvar . "<BR>" );
echo ( "<A HREF=\"sess1.php\">sess1</A><BR>" );
echo ( "<FORM ACTION=\"sess2.php\">" );
echo ( "<INPUT TYPE=\"TEXT\" NAME=\"myvar\">" );
echo ( "<INPUT TYPE=\"SUBMIT\">" );
?>
