使用多个字段搜索MySQL表

I have this HTML form which has so many fields that someone can use to query data from MySQL table using multiple conditions. The form has select boxes, text boxes and check boxes, and date inputs.

I have this function which is ineffective

public function search(Request $request)
    {

        // loop through the defined fields
        foreach($this->fields as $field){
            // if the field is set and not empty
            if(is_array($request->get($field))){
                foreach ($request->get($field) as $value) {
                    $this->conditions[] = "`$field` = '" . $value . "'";
                }
            } else {
                 if(isset($_POST[$field]) && $request->get($field) != '') {

                    $data = $request->get($field);

                    if($field == 'bf_ref_no'){
                        $data = is_numeric( substr($request->get($field), 0, 2) )  ? 'BF'.$request->get($field)  : $request->get($field) ;
                    }

                    $this->conditions[] = "`$field` = '" . $data . "'";
                }
            }

        }

        // builds the query
        $query = "SELECT invoices.id as inv_id, invoices.created_at as inv_date, invoices.amount_paid, invoices.amount, csv_data_final.* FROM csv_data_final 
        LEFT JOIN invoices ON invoices.parent_id = csv_data_final.id ";
        // if there are conditions defined
        if(count($this->conditions) > 0) {
            // append the conditions
            $query .= "WHERE " . implode (' AND ', $this->conditions); // you can change to 'OR', but I suggest to apply the filters cumulative
        }

        $results = DB::select( $query );

        $borders = DB::table('borders')->orderBy('id', 'DESC')->get();

        return view('track.track-withdata', compact('results', 'borders'));

    }

This code doesn't work for dates using BETWEEN keyword.