使用CodeIgniter通过两个参数编号搜索数据

I have problems with where CodeIgniter on the query, which I want to find the data between the two parameters. like the example below.

Controllers

public function search_genus() {    
    $data = array(
        'find_kebun' => $this->my_model->find(),
        'content' =>'my_view'
    );      
    $this->load->view('layout/wrapper', $data);
}

Models

public function find() {    
    $search = $this->input->post('param');

    $A = "1 - 10";
    $B = "11- 15";

    if ($search = $A ) {
            $query = $this->db->select('*')
                              ->from('my_tables')
                              ->where('genus', 1 > 10)
                              ->get();      
            return $query->result();    
    }else if ($search = $B ) {
            $query = $this->db->select('*')
                              ->from('my_tables')
                              ->where('genus', 11 > 15)
                              ->get();      
            return $query->result();    
    }

}

Views

<form action="<?php echo base_url(); ?>/search_genus"   method="post" enctype="multipart/form-data">
    <select name="param">
        <option value="A">1 - 10</option>
        <option value="B">11 - 15</option>
    </select>

    <button class="btn btn-default" type="submit">
</form>

after I run error at where how to solve?

Try this - Controller:

public function search_genus() {   
    $search = $this->input->post('param'); 
    $data = array(
        'find_kebun' => $this->my_model->find($search ),
        'content' =>'my_view'
    );      
    $this->load->view('layout/wrapper', $data); 
}

And Model

 public function find($search) {    

        $A = "1 - 10";
        $B = "11- 15";
if ($search == "A" ) {
            $query = $this->db->select('*')
                              ->from('my_tables')
                              ->where('genus', 1 > 10)
                              ->get();      
            return $query->result();    
    }else if ($search == "B" ) {
            $query = $this->db->select('*')
                              ->from('my_tables')
                              ->where('genus', 11 > 15)
                              ->get();      
            return $query->result();    
    }