mysql_connect(): Connection using old (pre-4.1.1) authentica_MySQL
做了一下mysql升级，开发机上mysql升级到5.6版本，结果连接一些低版本的mysql服务器报出如下异常：
Warning: mysql_connect(): Connection using old (pre-4.1.1) authentication protocol refused (client option 'secure_auth' enabled)
异常原因在于服务器端的密码管理协议陈旧，使用的是旧有的用户密码格式存储；但是客户端升级之后采用了新的密码格式。mysql5.6版本遇到这种不一致的情况就会拒绝连接。
详见mysql手册“Server Command Options”一节中“--secure-auth"选项的说明：http://dev.mysql.com/doc/refman/5.6/en/server-options.html#option_mysqld_secure-auth
解决方法有如下三种：
1、服务器端升级启用secure_auth选项；
2、客户端连接时off掉secure_auth，即连接时加上--secure_auth=off，如：mysql -p10.51.1.11 -P3308 -uroot --secure_auth=off
3、找到对应的mysql用户把密码改为新的加密方式，PASSWORD(‘your password')，如：
SET PASSWORD FOR root=PASSWORD('123456');
对于方法二，使用在程序做相应mysql配置即可，以php为例，在php.ini中设置secure_auth=off
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