PDO don't know which is mysql server charset?

hi, everybody! I encountered a problem using the PDO: My mysql charset is utf-8, when using PDO's prepare () and statement’s execute() methods, there is not the correct encoding resultset: $ Statement = $ pdo-> prepare ("SELECT * FROM guests ORDER BY?"); $ Statement-> execute (array ('lname')); while ($ row = $ statement-> fetch (PDO:: FETCH_ASSOC)) ( echo $ row ['fname']. "". $ row ['lname']; ) But when I was make charset_set_results to be gbk, everything was normal: $ Pdo-> exec ('SET character_set_results = gbk'); If PDO don't know which charset is fit to me,it will use default charset(utf-8)?This is really mysql server charset! Anybody help me?Thanks! PS: I am using wamp (php5.3.1) -- cleverpig(Dan) Location: Beijing Address: Room 4018,No.A2 South Avenue Fuxingmen Beijing,P.R.China Zipcode: 100031 MSN: great_liudan@hotmail.com QQ: 149291732 Skype: cleverpigatmatrix Facebook ID:cleverpig Blog: cleverpig.name/dan/ Tags: del.icio.us/cleverpig Twitter: twitter.com/cleverpig 新浪微博: t.sina.com.cn/cleverpig Organization: www.beijing-open-party.org Organ@Facebook: http://www.facebook.com/group.php?gid=8159558294