WordPress Search & Filter amend for url parameter

/* POST TYPES */
if((isset($_POST[SF_FPRE.'post_types']))&&($this->has_form_posted))
{
    $the_post_types = ($_POST[SF_FPRE.'post_types']);

    //make the post an array for easy looping
    if(!is_array($the_post_types))
    {
        $post_types_arr[] = $the_post_types;
    }
    else
    {
        $post_types_arr = $the_post_types;
    }

    $num_post_types = count($post_types_arr);

    for($i=0; $i<$num_post_types; $i++)
    {
        if($post_types_arr[$i]=="0")
        {
                $post_types_arr[$i] = "all";
        }
    }

    if(count($post_types_arr)>1)
    {
        $operator = ","; //default behaviour

        //check to see if an operator has been specified - only applies with fields that use multiple selects such as checkboxes or multi selects
        /*if(isset($_POST[SF_FPRE.'post_types_operator']))
        {
                if($_POST[SF_FPRE.'post_types_operator']=="and")
                {
                        $operator = "+";
                }
                else if($_POST[SF_FPRE.'post_types_operator']=="or")
                {
                        $operator = ",";
                }
                else
                {
                        $operator = "+";
                }
        }*/

        $post_types = implode($operator,$post_types_arr);

        if(!$this->hasqmark)
        {
                $this->urlparams .= "?";
                $this->hasqmark = true;
        }
        else
        {
                $this->urlparams .= "&";
        }
        $this->urlparams .= "post_types=".$post_types;

    }
    else
    {
        $operator = ","; //default behaviour

        $post_types = implode($operator,$post_types_arr);

        if(!$this->hasqmark)
        {
                $this->urlparams .= "?";
                $this->hasqmark = true;
        }
        else
        {
                $this->urlparams .= "&";
        }

        $this->urlparams .= "post_type=".$post_types;
    }
}