因为本站的前端展示放弃使用WordPress博客系统的，而是改用自己的vue服务端渲染了，在保留原来的链接地址（比如https://www.daozhao.com/8531.html）不变的情html况下，只能更改WordPress里面的固定链接了，只能委屈WordPress使用https://www.daozhao.com/8531.php这的链接了。 但是我这样的改造对于WordPress系统里面的插件等而已，它们并不知情，它们会继续用WordPress里面的方法get_permalink($post)来获取固定链接。比如我现在提到的生成sitemap插件google-sitemap-generator，我就需要简单改造下了，让生成的sitemap.xml里面显示的博文链接为xxx.html。

于是决定小改wordpress生成sitemap插件google-sitemap-generator。

// plugin/google-sitemap-generator/sitemap-builder.php
foreach($posts AS $post) {

                    //Fill the cache with our DB result. Since it's incomplete (no text-content for example), we will clean it later.
                    //This is required since the permalink function will do a query for every post otherwise.
                    //wp_cache_add($post->ID, $post, 'posts');

                    //Full URL to the post
                    $permalink = get_permalink($post);

                    //Exclude the home page and placeholder items by some plugins. Also include only internal links.
                    if(
                        !empty($permalink)
                        && $permalink != $home
                        && $post->ID != $homePid
                        && strpos( $permalink, $home) !== false
                    ) {

                        //Default Priority if auto calc is disabled
                        $priority = ($postType == 'page' ? $defaultPriorityForPages : $defaultPriorityForPosts);

                        //If priority calc. is enabled, calculate (but only for posts, not pages)!
                        if($priorityProvider !== null && $postType == 'post') {
                            $priority = $priorityProvider->GetPostPriority($post->ID, $post->comment_count, $post);
                        }

                        //Ensure the minimum priority
                        if($postType == 'post' && $minimumPriority > 0 && $priority < $minimumPriority) $priority = $minimumPriority;

                        //ADdd the URL to the sitemap
                        $gsg->AddUrl(
                            $permalink,
                            $gsg->GetTimestampFromMySql($post->post_modified_gmt && $post->post_modified_gmt != '0000-00-00 00:00:00'? $post->post_modified_gmt : $post->post_date_gmt),
                            ($postType == 'page' ? $changeFrequencyForPages : $changeFrequencyForPosts),
                            $priority, $post->ID);
                    }

                    //Why not use clean_post_cache? Because some plugin will go crazy then (lots of database queries)
                    //The post cache was not populated in a clean way, so we also won't delete it using the API.
                    //wp_cache_delete( $post->ID, 'posts' );
                    unset($post);
                }

里面的AddUrl方法的第一个参数就是$permalink，顺着一步一步往前看，

// plugin/google-sitemap-generator/sitemap-core.php
public function AddUrl($loc, $lastMod = 0, $changeFreq = "monthly", $priority = 0.5, $postID = 0) {
        //Strip out the last modification time if activated
        if($this->GetOption('in_lastmod') === false) $lastMod = 0;
        $page = new GoogleSitemapGeneratorPage($loc, $priority, $changeFreq, $lastMod, $postID);

        do_action('sm_addurl', $page);

        if($this->simMode) {
            $caller = $this->GetExternalBacktrace(debug_backtrace());

            $this->simData["content"][] = array(
                "data" => $page,
                "caller" => $caller
            );
        } else {
            $this->AddElement($page);
        }
    }

还是的形参$loc就是上面说的$permalink，AddUrl通过GoogleSitemapGeneratorPage的构造函数获得了实例$page,后续的操作都是传递$page完成，所以我们可以看看这个构造函数做了什么。

public function __construct($url = "", $priority = 0.0, $changeFreq = "never", $lastMod = 0, $postID = 0) {
    $this->SetUrl($url);
    $this->SetProprity($priority);
    $this->SetChangeFreq($changeFreq);
    $this->SetLastMod($lastMod);
    $this->SetPostID($postID);
}

/**
 * Returns the URL of the page
 *
 * @return string The URL
 */
public function GetUrl() {
    return $this->_url;
}

/**
 * Sets the URL of the page
 *
 * @param string $url The new URL
 */
public function SetUrl($url) {
  $oldUrl = str_replace(".php",".html", (string) $url);
  $this->_url = $oldUrl;
}

可以看到这个的SetUrl方法是设置实例的_url属性的，我们在这里劫持下就可以了。

今天发现自己还有个百度推送插件baidu-submit-link也需要做相应的调整，这样一个一个的改当然很烦了，于是就想着直接从源头改了算了，那就是直接改WordPress的get_permalink方法。

// wp-includes/link-template.php
function get_permalink( $post = 0, $leavename = false ) {
...
    $permalink = str_replace(".php",".html", $permalink);

    /**
     * Filters the permalink for a post.
     *
     * Only applies to posts with post_type of 'post'.
     *
     * @since 1.5.0
     *
     * @param string  $permalink The post's permalink.
     * @param WP_Post $post      The post in question.
     * @param bool    $leavename Whether to keep the post name.
     */
    return apply_filters( 'post_link', $permalink, $post, $leavename );
}

优点就是以后再也不用一个一个的改插件或者其它需要获取固定链接的地方了，缺点就是以后每次升级WordPress之后都要进行这部分的调整。