用户输入验证，客户端还是服务器端? [PHP/JS]

在使用JS将用户输入发送到服务器或使用PHP将其发送到服务器端之前，验证用户输入是否更好?还是只是为了安全起见才值得做这两者?

Is it better to validate user input before it's sent to the server with JS or server side with PHP? Or maybe it's worth doing both just to be on the safe side?

我正在创建一个站点(目前非常简单)，该站点具有成员区域/管理区域/等.目前，我只有用户名和密码作为用户输入，将来还会有更多(电子邮件，地址等)，但是检查数据的最佳做法是什么?

I'm creating a site (very simple at the moment) that has a members area/admin area/etc. At the moment i only have user input of Username and Password, in the future there will be more (email, address, etc), but whats the best practice of checking the data?

在用户正确之前，我是否向其中抛出"if ... else"语句?或者，对于用户输入的每个值，可能有单独的变量，如果正确或错误，则将其设置为true或false? (例如电子邮件验证，以确保其为电子邮件格式)

Do i throw a load of 'if...else' statements at it until the user gets it right? Or maybe have separate variables for each value entered by the user and set it to true or false if it's correct or wrong? (like e-mail validation to make sure it's in an email format)

有很多方法可以做到，但是您会建议哪些呢?当我可以用10行完成这项工作时，我不想写50行代码...如果可以的话:p

There are a lot of ways to do it, but which ones you would suggest? I don't want to be writing 50 lines of code when i could do the job in 10 lines...if that makes sense :p

任何帮助将不胜感激，谢谢！ :)

Any help would be appreciated, thanks! :)