$this->load->library('form_validation');

        $this->form_validation->set_rules('book_title', 'Title', 'required|xss_clean|max_lenth[50]');
        $this->form_validation->set_rules('book_type', 'Book Type', 'required|xss_clean');
        $this->form_validation->set_rules('book_audience', 'Audience', 'required|xss_clean');

        if ($this->input->post('book_type') = 'Paid') {

            $this->form_validation->set_rules('book_price', 'Price/Donation Amount', 'required|xss_clean|numeric|less_than[10.01]|greater_than[0]');

        } else {

            $this->form_validation->set_rules('book_price', 'Price/Donation Amount', 'required|xss_clean|numeric|less_than[10.01]');

        }


// This is the error I'm getting:
// Fatal error: Can't use method return value in write context in /home/ezpublis/public_html/dev/bonfire/application/controllers/publish.php on line 46

// Line 46 = if ($this->input->post('book_type') = 'Paid') {