Validate URLs by extending CodeIgniter Form Validation Library

MY_Form_Validation.php

# My Form Validation Class
# Save this in 'core' folder under 'application' folder

class MY_form_validation extends CI_form_validation {
    function valid_url($str){
        if(filter_var($str, FILTER_VALIDATE_URL)) {
            return TRUE;
        } else {
            return FALSE;  
        }
    }
}

# In Controller

$this->form_validation->set_rules('field_name', 'field_label', 'valid_url');