Starting MVC PHP - am I doing it right?
Yes, you understood how MVC works, and you are doing it right. The helper functions such as redirect() are in the correct classes. A few comments on the code itself:


I'd recommend to add an exit; statement after sending headers in redirect(). It will be easier to understand the code, since you can now think of the redirect() as a return, which will help you avoid mistakes.
Don't store your password in plain text.
Symply use return $this-&gt;linhas == 1; at the end of your login function.
Your model class simply translates the PDO interface into Portuguese, this is not an interesting layer of abstraction in my book. :)
Declare the variables you use, eg. $this-&gt;stm or $this-&gt;conn.
You are probably going to want an easier way to make requests when you will have dozens of them, but right now it's OK.