Pretty URI - Enhance internal URIs (usefull when a migration is planned).

pretty-uri.php

<?php
/*
Plugin Name: Pretty URI
Description: Enhance internal URIs (usefull when a migration is planned).
Version:     1.0
Author:      Seebz
Author URI:  http://seebz.net/
*/


// Is WP on server root ?
if ( ! pu_is_wp_on_root() ) {
	return;
}


/*
 * Filters
 */

// Post content/excerpt (on save)
add_filter( 'content_save_pre', 'pu_filter_post_content' );
add_filter( 'excerpt_save_pre', 'pu_filter_post_content' );
function pu_filter_post_content( $content ) {
	$content = pu_replace_links_uri( $content );
	$content = pu_replace_images_uri( $content );
	return $content;
}

// Menu items (on display)
add_filter( 'wp_nav_menu_items', 'pu_filter_menu_items' );
function pu_filter_menu_items( $items ) {
	$items = pu_replace_links_uri( $items );
	return $items;
}

// Attachment URL
add_filter( 'wp_get_attachment_url', 'pu_filter_attachment_url' );
function pu_filter_attachment_url( $url ) {
	$url = pu_replace_content_uri( $url );
	return $url;
}


/*
 * Utility
 */

// Is WP installed on server root
function pu_is_wp_on_root() {
	$wp_url = get_site_url();
	$wp_path = parse_url( $wp_url, PHP_URL_PATH );
	return ( ! $wp_path || $wp_path == '/' );
}

// Replace URIs in links (<a>)
function pu_replace_links_uri( $content ) {
	$pattern = '`<a[^>]*>`';
	if ( preg_match_all( $pattern, $content, $matches ) ) {
		foreach( $matches[0] as $m ) {
			$content = str_replace( $m, pu_replace_content_uri( $m ), $content );
		}
	}
	return $content;
}

// Replace URIs in images (<img>)
function pu_replace_images_uri( $content ) {
	$pattern = '`<img[^>]*>`';
	if ( preg_match_all( $pattern, $content, $matches ) ) {
		foreach( $matches[0] as $m ) {
			$content = str_replace( $m, pu_replace_content_uri( $m ), $content );
		}
	}
	return $content;
}

// Replace URIs in content
function pu_replace_content_uri( $content ) {
	$search = get_site_url( null, '/' );
	$replace = '/';
	return str_replace( $search, $replace, $content );
}