检查函数的内容并检查它运行两次吗？

This is kind of a stupid question but I'm in doubt:

I'm checking below that a function (which queries my db) doesn't return NULL and redirecting if it does.

If it doesn't I then assign it to an array.

In the code below, is the query ran twice?

    if (!$this->review_model->GetReview($data['review_type'], $data['review_id'])) {
        redirect();
    }

    $data['review'] = $this->review_model->GetReview($data['review_type'], $data['review_id']);

Yes, it runs twice if not redirected...

Do this

$data['review'] = $this->review_model->GetReview($data['review_type'], $data['review_id']);
if (!$data['review']) {
    redirect();
}

For your question, No, once redirect() method called, further line not executed.

But your checking is not good. you can change it is as following

$data['review'] = $this->review_model->GetReview($data['review_type'], $data['review_id']);

if(!$data['review']){
  redirect();
}