simplistik

If you’re interested I have a fully working version (so far as I can tell) I based it off of your 1.3 code though and not your 1.3.1 (which is what is in the above posts) code. I know you put some work into 1.3.1.

I did that because 1.3 worked in terms of class placement, just not on the last parent item. This should properly add the “last” class to the last parent item, while maintaining all it’s other functionality, and keeping true to code you wrote and are familar with. Also includes the 2.8 register updates with legacy support (I think, we don’t have any blogs under 2.8). Tweak it as you will … or don’t use it at all. We just needed the plug-in to work by the end of today so I took the liberty of doing it, until an official patch. Doesn’t have the uninstall code added to 1.3.1 though.

add_filter('wp_list_pages','c_wp_lp_filter');
add_action('admin_menu', 'c_wp_lp_add_menus');

$c_wp_lp_options = array('c_wp_lp_prefix' => 'Class prefix',
                         'c_wp_lp_sep' => 'Class separator',
                         'c_wp_lp_attr' => 'Attribute',
                         'c_wp_lp_first_class' => 'Class to add to first element',
                         'c_wp_lp_last_class' => 'Class to add to last element');

add_action('admin_init', 'classy_wp_list_pages_init' );
function classy_wp_list_pages_init() {
	global $c_wp_lp_options;

	if( function_exists( 'register_setting' ) ) {

		foreach ( $c_wp_lp_options as $k => $v ) {
			register_setting( 'classy-wp-list-pages' , $k );
		}

	}
}

$c_wp_lp_values = array();

/**************************************

 wp_list_pages() filter

***************************************/
function c_wp_lp_filter_callback($matches) {
	global $c_wp_lp_values;

	$prefix = (strlen($c_wp_lp_values['c_wp_lp_prefix'])) > 0 ?
	              $c_wp_lp_values['c_wp_lp_prefix'] . $c_wp_lp_values['c_wp_lp_sep'] :
	              '';

	// build the identifier
	//  - strip trailing and preceding slashes
	//  - replace the remaining slashes with the separator (from get_options())
	$identifier = '';

	if( $matches[4] && !empty($matches[4]) ) {
		$identifier = preg_replace('/(^\/|\/$)/', '', $matches[4]);
		$identifier = str_replace('/', $c_wp_lp_values['c_wp_lp_sep'], $identifier);
	} else { // if the url is blank, this is the homepage
		$identifier = 'frontpage';
	}

	$identifier = $prefix . $identifier;

	$filtered = '';

	if( $c_wp_lp_values['c_wp_lp_attr'] == 'id' ) {
		$filtered = sprintf("<li id=\"%s\"%s><a href=\"%s\"", $identifier, $matches[1], get_option('home') . '/' . $matches[4]);
	} else {
		// append any existing classes and trim out extra spaces
		$class = $identifier . ' ' . trim($matches[2]);
		$class = preg_replace('/[ ]+/', ' ', $class);
		$filtered = sprintf("<li class=\"%s\"><a href=\"%s\"", $class, get_option('home') . '/' . $matches[4]);
	}

	return $filtered;
}

function c_wp_lp_filter($content) {
	global $c_wp_lp_values;

	// load plugin options from the database
	$c_wp_lp_values = c_wp_lp_get_values();

	// escape the blog's base URL
	$url = preg_replace(array('/\//', '/\./', '/\-/'), array('\/', '\.', '\-'), get_option('home'));

	$pattern = '/<li( class=\"([\w\s_\-]+)\")?><a href=\"' . $url . '(\/([\w\-_\/]+))?"/i';

	$content = preg_replace_callback($pattern, "c_wp_lp_filter_callback", $content);

	// add class to first list item
	if ( !empty($c_wp_lp_values['c_wp_lp_first_class']) ) {
		$content = preg_replace('/(<ul>|^)[\s]*<li([\s]*id=("[\w_-]+"|\'[\w_-]+\')[\s]*)? class="/i',
		                        "$1<li$2 class=\"" . $c_wp_lp_values['c_wp_lp_first_class'] . ' ',
		                        $content,
		                        -1);
	}

	// add class to last list item
	if ( !empty($c_wp_lp_values['c_wp_lp_last_class']) ) {
		// reverse the string to make things easier
		$content_rev = strrev($content);

		$pages = get_pages('sort_order=DESC&sort_column=menu_order&parent=0&number=1');
		$last_page = $pages[0];
		$last_page = $last_page->post_name;

		// match an <li... next to a </ul> or and EOL
		$content_rev = preg_replace('/(\A|>lu\/<)[\s](.*)"=ssalc([\s]*("[\w_-]+"|\'[\w_-]+\')=di[\s]*)? il</imu',
		                            "$1$2 " . strrev($c_wp_lp_values['c_wp_lp_last_class']) . "\"=ssalc$3 il<",
		                            $content_rev,
		                            -1);

		$content = strrev($content_rev);

		$content = preg_replace(
			array('/<li[\s]id="' . $last_page . '"[\s]class="(.*)">/i', '/<li[\s]id="' . $last_page . '"[\s]class="last[\s](.*)">/i'),
			array('<li id="' . $last_page . '" class="last $1">','<li id="' . $last_page . '" class="last $1">'),
			$content
		);
	}

	return $content;
}

/**************************************

 Menu functions

***************************************/
function c_wp_lp_add_menus() {
	add_options_page('Classy wp_list_pages Options', 'Classy wp_list_pages', 8, 'c_wp_lp_options', 'c_wp_lp_options_page');
}

// read this plugin's options from the database
function c_wp_lp_get_values() {
	global $c_wp_lp_options;

	$opt_values = array();

	foreach( $c_wp_lp_options as $k => $v )
		$opt_values[$k] = get_option($k);

	// default value for separator is an underscore
	if(strlen(trim($opt_values['c_wp_lp_sep'])) < 1)
		$opt_values['c_wp_lp_sep'] = '_';

	// default value for attribute is ID
	if(strlen(trim($opt_values['c_wp_lp_attr'])) < 1)
		$opt_values['c_wp_lp_attr'] = 'id';

	return $opt_values;
}

function c_wp_lp_options_page() {
	global $c_wp_lp_options;

    echo '<div class="wrap">';

    echo "<h2>" . __( 'Classy wp_list_pages Options', 'c_wp_lp_trans_domain' ) . "</h2>";

    // options form

    ?>

<form method="post" action="options.php">
<?php global $wp_version;?>
<?php if ( version_compare( $wp_version, '2.8', '<' ) ): ?>
	<?php  wp_nonce_field('update-options'); ?>
	<input type="hidden" name="action" value="update" />
	<input type="hidden" name="page_options" value="c_wp_lp_attr,c_wp_lp_prefix,c_wp_lp_sep,c_wp_lp_first_class,c_wp_lp_last_class" />
<?php else: ?>
	<?php settings_fields('classy-wp-list-pages'); ?>
<?php endif; ?>

	<p>Should the identifier be applied to the class or ID attribute?<br /><br />
		<?php _e("Attribute:", 'c_wp_lp_trans_domain' ); ?>
		<select name="c_wp_lp_attr">
			<option value="id"<?php echo get_option('c_wp_lp_attr') == 'id' ? ' selected="selected"' : ''; ?>>ID</option>
			<option value="class"<?php echo get_option('c_wp_lp_attr') == 'class' ? ' selected="selected"' : ''; ?>>Class</option>
		</select>
	</p><hr />

	<p>An optional string appended to the beginning of the generated identifier (letters and numbers only).<br /><br />
	<?php _e("Prefix:", 'c_wp_lp_trans_domain' ); ?>
		<input type="text" name="c_wp_lp_prefix" value="<?php echo get_option('c_wp_lp_prefix'); ?>" size="5">
	</p><hr />

	<p>What character should separate each token in the identifier?<br /><br />
	<?php _e("Token separator:", 'c_wp_lp_trans_domain' ); ?>
		<select name="c_wp_lp_sep">
			<option value="-"<?php echo $opt_values['c_wp_lp_sep'] == '-' ? ' selected="selected"' : ''; ?>>Dash (-)</option>
			<option value="_"<?php echo $opt_values['c_wp_lp_sep'] == '_' ? ' selected="selected"' : ''; ?>>Underscore (_)</option>
		</select>
	</p><hr />

	<p>	<?php _e("Class to add to the first list item:", 'c_wp_lp_trans_domain' ); ?>
		<input type="text" name="c_wp_lp_first_class" value="<?php echo get_option('c_wp_lp_first_class'); ?>" size="25">
	</p><hr />

	<p>	<?php _e("Class to add to the last list item:", 'c_wp_lp_trans_domain' ); ?>
		<input type="text" name="c_wp_lp_last_class" value="<?php echo get_option('c_wp_lp_last_class'); ?>" size="25">
	</p><hr />

	<p class="submit">
		<input type="submit" name="Submit" value="<?php _e('Update Options »', 'c_wp_lp_trans_domain' ) ?>" />
	</p>
</form>
</div>

<?php } ?>

Not a problem I like to help where I can 🙂