2 $this->input->post :one is empty and the other returns ok

Maybe because you have spaces at the wrong places (name and value) :

Code:

<input type="text" class="form-control" id="cnometur" name="cnometur "placeholder="Nome da Turma" value=""required>

Should be:

Code:

<input type="text" class="form-control" id="cnometur" name="cnometur" placeholder="Nome da Turma" value="" required>

OHHHH..my god! Many days of home office, stressed ... and that was exactly the mistake! A space at the end .... kkkkkkkk

THANK YOU !