wp-pagenavi not working

<?php
#Page Navi

function page_navi($before = '', $after = '') {
	global $wpdb, $wp_query;
	
	$request = $wp_query->request;
	$posts_per_page = intval(get_query_var('posts_per_page'));
	$paged = intval(get_query_var('paged'));
	$numposts = $wp_query->found_posts;
	$max_page = $wp_query->max_num_pages;
	
	if(empty($paged) || $paged == 0) {
		$paged = 1;
	}
	$pages_to_show = 5;
	$pages_to_show_minus_1 = $pages_to_show-1;
	$half_page_start = floor($pages_to_show_minus_1/2);
	$half_page_end = ceil($pages_to_show_minus_1/2);
	$start_page = $paged - $half_page_start;
	if($start_page <= 0) {
		$start_page = 1;
	}
	$end_page = $paged + $half_page_end;
	if(($end_page - $start_page) != $pages_to_show_minus_1) {
		$end_page = $start_page + $pages_to_show_minus_1;
	}
	if($end_page > $max_page) {
		$start_page = $max_page - $pages_to_show_minus_1;
		$end_page = $max_page;
	}
	if($start_page <= 0) {
		$start_page = 1;
	}
	
	echo $before.'<center><div class="page_navi">'."\n";
	if ($start_page >= 2 && $pages_to_show < $max_page) {
		$first_page_text = "First";
		echo '<a href="'.get_pagenum_link().'" title="'.$first_page_text.'">'.$first_page_text.'</a>';
	}
	previous_posts_link('«');
	for($i = $start_page; $i  <= $end_page; $i++) {						
		if($i == $paged) {
			echo '<span class="current">'.$i.'</span>';
		} else {
			echo '<a href="'.get_pagenum_link($i).'">'.$i.'</a>';
		}
	}
	next_posts_link('»');
	if ($end_page < $max_page) {
		$last_page_text = "Last";
		echo '<a href="'.get_pagenum_link($max_page).'" title="'.$last_page_text.'">'.$last_page_text.'</a>';
	}
	echo '</div></center>'.$after."\n";
}
?>

  <div class="page_navi">
    <?php page_navi(); ?>
  </div>