MD5 to protect password keeps changing hash

Question

I have a code to protect the password of the very basic database. However to log in I am always using the following:

$email = $post['email'];
$senha = md5($post['senha']);
return $this->model->Query('SELECT * FROM 
usuario WHERE email = ? AND senha = ? AND deletado = ? 
ORDER BY id ASC', array($email, $senha, 0));

Only md5 started to show a behavior that had not noticed before, it is changing the hash constantly in the login, something that had never happened before, perhaps due to lack of observation.

How do I make the database hash to match the login hash ?

Att.