CI4 csrf_field not generate same value as csrf_hash

I'm trying to implement csrf validation in my form.

based on my understanding, we just compare the csrf hash from view/post with the csrf in backend/controller.

so, i tried to use 

Code:

<?= csrf_field() ?>

 in my view page, then do some comparison

Code:

if ($this->request->getPost(csrf_token()) === csrf_hash()) {
#do some stuff
}

result: the hash value is different.

but it wont be an issue if i use 

Code:

csrf_token() and csrf_hash()

 in the form. the hash generated always same.

how to solve this or do the validation bt using the csrf_field? as per documentation, it only stated the way we can retrieve the value with the same exact thing that I've done.

fyi, I'm not using 

Code:

form_open()

 as i would prefer to do the html by myself with some bootstrap.