RADIO

CODEIGNITER

 <input type="radio" name="gender" value="male">Male</input>
 <input type="radio" name="gender" value="female">Female</input>

 $this->load->library('form_validation');
    $this->form_validation->set_rules('gender', 'Gender', 'required'); // This will check if gender is selected.
    if ($this->form_validation->run()) {
      $gender = $this->input->post('gender'); // This will contain "male" or "female"
    }
    else {
      $error = validation_errors();
 }

PHP

<fieldset>
   <legend>Choose Business Type:</legend><br>
   <input type="radio" name="businessType" value="1">
   <input type="radio" name="businessType" value="2">
   <input type="radio" name="businessType" value="3">
</fieldset>

untuk menangkap datanya : 

   $businessType = $this->input->post("businessType");