Array
(
 [0] => stdClass Object
  (
   [username] => 张三
   [password] => DQ9uqQW2+UudOsZpQMnyvGG9L+RHZB6LRzBVDvAEL9uOBNf2zTWUnykhZFjhbzCH+LrSslRx9eSqU/n3gSLSUA==
  )

 [1] => stdClass Object
  (
   [username] => 李四
   [password] => 2P/3j50ibk1BYmjHL+7/tt0d6LuOQMN9m8klXJCZbcajQtH5749jFTtH17WxiBZ9p425b4KIV/Xdv/7Bu4pJAQ==
  )

 [2] => stdClass Object
  (
   [username] => 王五
   [password] => caq8lq0l6uxJPRx+sCBsBFUojSF+ox98gwO6c/AquXQ/y/aj/l/ziEGsXRSV+olcK7iKOJJ4IZZvX8DMPWZRRA==
  )

 [3] => stdClass Object
  (
   [username] => 赵六
   [password] => taXp4jX0vO3VoFLyANfGrSjzy76WQQHMnzYAN9CyI20uKxLFMScXrFR3P525eImy0pG5zk8btBJoS/RyMxzJGQ==
  )

)

foreach ($pass as $key) {
 $key->username = iconv('UTF-8', 'GBK', $key->username);
}
asort( $pass );
foreach ($pass as $key) {
 $key->username = iconv('GBK', 'UTF-8', $key->username);
}