As I'm not a big fan of Wordpress plug—ins, and I wanted to use a normal page navigation, not just the default “Previous posts” and “Next posts”, I decided to play around a bit and create my own paging navigation, or pagination.

Preparation

An example of the navigation

First, I wrote on a piece of paper which links I need: first page, last page, next page, previous page and the links with the page numbers. Next, I needed to see what functions are already in Wordpress, to reuse as much as I can. After a little searching, I found that the functions for the default navigation are located in the link-template.php file, under the wp-includes folder. There are the functions for the next and previous pages, and the function that creates the URL. Furthermore, I wanted a sliding pagination (like Yahoo has on it's search page), 'cause it's easy to use and looks cool.

The function

So, let's take a look at the code. I called the function simply get_pagination; it's quite self—describing. I put it in the link-template.php file, that way, all functions for navigation are in one place.

/**
* A pagination function
* @param integer $range: The range of the slider, works best with even numbers
* Used WP functions:
* get_pagenum_link($i) - creates the link, e.g. http://site.com/page/4
* previous_posts_link(' « '); - returns the Previous page link
* next_posts_link(' » '); - returns the Next page link
*/
function get_pagination($range = 4){
  // $paged - number of the current page
  global $paged, $wp_query;
  // How much pages do we have?
  if ( !$max_page ) {
    $max_page = $wp_query->max_num_pages;
  }
  // We need the pagination only if there are more than 1 page
  if($max_page > 1){
    if(!$paged){
      $paged = 1;
    }
    // On the first page, don't put the First page link
    if($paged != 1){
      echo "<a href=" . get_pagenum_link(1) . "> First </a>";
    }
    // To the previous page
    previous_posts_link(' « ');
    // We need the sliding effect only if there are more pages than is the sliding range
    if($max_page > $range){
      // When closer to the beginning
      if($paged < $range){
        for($i = 1; $i <= ($range + 1); $i++){
          echo "<a href='" . get_pagenum_link($i) ."'";
          if($i==$paged) echo "class='current'";
          echo ">$i</a>";
        }
      }
      // When closer to the end
      elseif($paged >= ($max_page - ceil(($range/2)))){
        for($i = $max_page - $range; $i <= $max_page; $i++){
          echo "<a href='" . get_pagenum_link($i) ."'";
          if($i==$paged) echo "class='current'";
          echo ">$i</a>";
        }
      }
      // Somewhere in the middle
      elseif($paged >= $range && $paged < ($max_page - ceil(($range/2)))){
        for($i = ($paged - ceil($range/2)); $i <= ($paged + ceil(($range/2))); $i++){
          echo "<a href='" . get_pagenum_link($i) ."'";
          if($i==$paged) echo "class='current'";
          echo ">$i</a>";
        }
      }
    }
    // Less pages than the range, no sliding effect needed
    else{
      for($i = 1; $i <= $max_page; $i++){
        echo "<a href='" . get_pagenum_link($i) ."'";
        if($i==$paged) echo "class='current'";
        echo ">$i</a>";
      }
    }
    // Next page
    next_posts_link(' » ');
    // On the last page, don't put the Last page link
    if($paged != $max_page){
      echo " <a href=" . get_pagenum_link($max_page) . "> Last </a>";
    }
  }
}

The “range” is the range of the sliding effect, i.e. how many numbers are shown besides the current number: if the range is 4, and the current page is 5, then the numbers 3, 4, 5, 6 and 7 are visible.

Usage

It's quite simple to use it: where the pagination is needed, just call the get_pagination() function, and it will show up. Add some CSS style to it, and your good to go.

Hope someone will find this useful :)

I just want to write some real examples. These regexps are (and always will be, 'cause I plan to write several posts on this topic) for the PHP's PCRE library. Here's a good PHP PCRE cheat sheet, it's an excellent resource for regexps. If you know nothing about regexps, first read this Wiki page.

Regexps for <a> tags

A common case is when you have a source of some web page and you want to parse out all the links from it.
An anchor tag goes something like this:

<a href="http://example.com/" title="Some website">Website</a>

Also it can have more attributes, like class, target etc. Knowing how it's built up, we can start writing a pattern, depending on what we want.
Here are some examples, some explanations are in the comments:

<?php
// Regexp examples for <a> tags

/**
* Different combinations...
* $matches_comb[0] contains the whole <a> tag
* $matches_comb[1] contains what's inside the "href" attribute
* $matches_comb[2] contains what's after <a> and before </a>
* with the "s" modifier mathces <a> tags that are broken in several lines,
* ie. matches <a> tags with newlines
* without the "s" modifier, matches only <a> tags without a newline
*/
preg_match_all(
    '#<a\s.*href=["\'](.*)["\'].*>(.*)</a>#isxU',
    $string,
    $matches_comb
);

/**
* Match only what's inside the href attributes...
*/
preg_match_all(
    '#<a\s.*href=["\'](.*)["\'].*>.*</a>#isxU',
    $string,
    $matches_href
);

/**
* Match only what's inside the href attirbutes,
* only when it starts with http:// and includes http://
* $mathces_href_http[0] contains some trash also, nevermind,
* $mathces_href_http[1] contains exactly what we need
*/
preg_match_all(
    '#<a\s.*href=["\'](http://.*)["\'].*>.*</a>#isxU',
    $string,
    $matches_href_http
);

/**
* Match all Email addresses - mailto:
*/
preg_match_all(
    '#"mailto:(.*)"#',
    $string,
    $matches_emails
);

?>

Play around with these patterns, see what's for what, experiment, that's the best way to learn regexps.
Do you have some more regexps for links? Some better ones than these here?
Happy hacking!