I ran into this myself. When using query strings, CodeIgniter should assume that you have other query string parameters (BUT, CI assumes that you use query string parameters to match your controller and method ...). I like to use the query string for things like filtering results, etc., Still using the basic routing parameters in the URI (like you).
I had to live with & in person, but I suppose you could expand the pagination library like this (long function, sorry):
class MY_Pagination extends CI_Pagination { function create_links() { // If our item count or per-page total is zero there is no need to continue. if ($this->total_rows == 0 OR $this->per_page == 0) { return ''; } // Calculate the total number of pages $num_pages = ceil($this->total_rows / $this->per_page); // Is there only one page? Hm... nothing more to do here then. if ($num_pages == 1) { return ''; } // Determine the current page number. $CI =& get_instance(); if ($CI->config->item('enable_query_strings') === TRUE OR $this->page_query_string === TRUE) { if ($CI->input->get($this->query_string_segment) != 0) { $this->cur_page = $CI->input->get($this->query_string_segment); // Prep the current page - no funny business! $this->cur_page = (int) $this->cur_page; } } else { if ($CI->uri->segment($this->uri_segment) != 0) { $this->cur_page = $CI->uri->segment($this->uri_segment); // Prep the current page - no funny business! $this->cur_page = (int) $this->cur_page; } } $this->num_links = (int)$this->num_links; if ($this->num_links < 1) { show_error('Your number of links must be a positive number.'); } if ( ! is_numeric($this->cur_page)) { $this->cur_page = 0; } // Is the page number beyond the result range? // If so we show the last page if ($this->cur_page > $this->total_rows) { $this->cur_page = ($num_pages - 1) * $this->per_page; } $uri_page_number = $this->cur_page; $this->cur_page = floor(($this->cur_page/$this->per_page) + 1); // Calculate the start and end numbers. These determine // which number to start and end the digit links with $start = (($this->cur_page - $this->num_links) > 0) ? $this->cur_page - ($this->num_links - 1) : 1; $end = (($this->cur_page + $this->num_links) < $num_pages) ? $this->cur_page + $this->num_links : $num_pages; // Is pagination being used over GET or POST? If get, add a per_page query // string. If post, add a trailing slash to the base URL if needed if ($CI->config->item('enable_query_strings') === TRUE OR $this->page_query_string === TRUE) { $this->base_url = str_replace('?&', '?', rtrim($this->base_url).'&'.$this->query_string_segment.'='); } else { $this->base_url = rtrim($this->base_url, '/') .'/'; } // And here we go... $output = ''; // Render the "First" link if ($this->first_link !== FALSE AND $this->cur_page > ($this->num_links + 1)) { $first_url = ($this->first_url == '') ? $this->base_url : $this->first_url; $output .= $this->first_tag_open.'<a '.$this->anchor_class.'href="'.$first_url.'">'.$this->first_link.'</a>'.$this->first_tag_close; } // Render the "previous" link if ($this->prev_link !== FALSE AND $this->cur_page != 1) { $i = $uri_page_number - $this->per_page; if ($i == 0 && $this->first_url != '') { $output .= $this->prev_tag_open.'<a '.$this->anchor_class.'href="'.$this->first_url.'">'.$this->prev_link.'</a>'.$this->prev_tag_close; } else { $i = ($i == 0) ? '' : $this->prefix.$i.$this->suffix; $output .= $this->prev_tag_open.'<a '.$this->anchor_class.'href="'.$this->base_url.$i.'">'.$this->prev_link.'</a>'.$this->prev_tag_close; } } // Render the pages if ($this->display_pages !== FALSE) { // Write the digit links for ($loop = $start -1; $loop <= $end; $loop++) { $i = ($loop * $this->per_page) - $this->per_page; if ($i >= 0) { if ($this->cur_page == $loop) { $output .= $this->cur_tag_open.$loop.$this->cur_tag_close; // Current page } else { $n = ($i == 0) ? '' : $i; if ($n == '' && $this->first_url != '') { $output .= $this->num_tag_open.'<a '.$this->anchor_class.'href="'.$this->first_url.'">'.$loop.'</a>'.$this->num_tag_close; } else { $n = ($n == '') ? '' : $this->prefix.$n.$this->suffix; $output .= $this->num_tag_open.'<a '.$this->anchor_class.'href="'.$this->base_url.$n.'">'.$loop.'</a>'.$this->num_tag_close; } } } } } // Render the "next" link if ($this->next_link !== FALSE AND $this->cur_page < $num_pages) { $output .= $this->next_tag_open.'<a '.$this->anchor_class.'href="'.$this->base_url.$this->prefix.($this->cur_page * $this->per_page).$this->suffix.'">'.$this->next_link.'</a>'.$this->next_tag_close; } // Render the "Last" link if ($this->last_link !== FALSE AND ($this->cur_page + $this->num_links) < $num_pages) { $i = (($num_pages * $this->per_page) - $this->per_page); $output .= $this->last_tag_open.'<a '.$this->anchor_class.'href="'.$this->base_url.$this->prefix.$i.$this->suffix.'">'.$this->last_link.'</a>'.$this->last_tag_close; } // Kill double slashes. Note: Sometimes we can end up with a double slash // in the penultimate link so we'll kill all double slashes. $output = preg_replace("#([^:])//+#", "\\1/", $output); // Add the wrapper HTML if exists $output = $this->full_tag_open.$output.$this->full_tag_close; return $output; } }