WordPress 主題開發常用快取 API 的講解與呼叫方案

經常看到有童鞋抱怨 WordPress 太耗資源了，其實 WordPress 作為世界上最流行的 php+mysql 建站系統，效能很不錯的。那麼為什麼還有一大堆童鞋抱怨 WordPress 太佔用伺服器資源呢？其實問題就出在 mysql 資料庫身上，由於 WordPress 大部分功能強大的外掛和主題模板都有很多資料需要儲存在資料庫中，而且由於一些主題開發者只追求功能強大而沒有考慮到網站執行的效能能問題，沒有一個良好的資料庫快取方案，所以導致了 WordPress 的臃腫。其實 WordPress 內部有著很好的快取機制 (Transients_API) 我們在開發主題時只需要呼叫 WordPress 快取機制即可。下面我舉幾個例子。

快取 WordPress 的選單 （menu）：PS 程式碼加入到 functions.php

<?php
function hh_cached_nav_menu( $args = array(), $prime_cache = false ) {
    global $wp_query;

    $queried_object_id = empty( $wp_query->queried_object_id ) ? 0 : (int) $wp_query->queried_object_id;
    $queried_object_id );

    $nav_menu_key = md5( serialize( $args ) );

    $my_args = wp_parse_args( $args );
    $my_args = apply_filters( 'wp_nav_menu_args', $my_args );
    $my_args = (object) $my_args;

    if ( ( isset( $my_args->echo ) && true === $my_args->echo ) || !isset( $my_args->echo ) ) {
        $echo = true;
    } else {
        $echo = false;
    }

    $skip_cache = false;
    $use_cache = ( true === $prime_cache ) ? false : true;

    if ( is_singular() ) {
        $skip_cache = true;
    } else if ( !in_array( $queried_object_id, hh_get_nav_menu_cache_objects( $use_cache ) ) ) {
        $skip_cache = true;
    }

    if ( true === $skip_cache || true === $prime_cache || false === ( $nav_menu = get_transient( $nav_menu_key ) ) ) {
        if ( false === $echo ) {
            $nav_menu = wp_nav_menu( $args );
        } else {
            ob_start();
            wp_nav_menu( $args );
            $nav_menu = ob_get_clean();
        }
        if ( false === $skip_cache )
            set_transient( $nav_menu_key, $nav_menu );
    }
    if ( true === $echo )
        echo $nav_menu;
    else
        return $nav_menu;
}


function hh_update_nav_menu_objects( $menu_id = null, $menu_data = null ) {
    hh_cached_nav_menu( array( 'echo' => false ), $prime_cache = true );
}
add_action( 'wp_update_nav_menu', 'hh_update_nav_menu_objects' );

function hh_get_nav_menu_cache_objects( $use_cache = true ) {
    $object_ids = get_transient( 'hh_nav_menu_cache_object_ids' );
    if ( true === $use_cache && !empty( $object_ids ) ) {
        return $object_ids;
    }




    $object_ids = $objects = array();

    $menus = wp_get_nav_menus();
    foreach ( $menus as $menu_maybe ) {
        if ( $menu_items = wp_get_nav_menu_items( $menu_maybe->term_id ) ) {
            foreach( $menu_items as $menu_item ) {
                if ( preg_match( "#.*/category/([^/]+)/?$#", $menu_item->url, $match ) )
                    $objects['category'][] = $match[1];
                if ( preg_match( "#.*/tag/([^/]+)/?$#", $menu_item->url, $match ) )
                    $objects['post_tag'][] = $match[1];
            }
        }
    }
    if ( !empty( $objects ) ) {
        foreach( $objects as $taxonomy => $term_names ) {
            foreach( $term_names as $term_name ) {
                $term = get_term_by( 'slug', $term_name, $taxonomy );
                if ( $term )
                    $object_ids[] = $term->term_id;
            }
        }
    }

    $object_ids[] = 0;

    set_transient( 'hh_nav_menu_cache_object_ids', $object_ids );
    return $object_ids;
}

快取標籤雲 （Tag cloud）：

$tag_cloud = get_transient( 'tag_cloud' );
if ( false === $tag_cloud || '' === $tag_cloud ){
    $args = array('echo' => false);
    $tag_cloud = wp_tag_cloud( $args );
    set_transient( 'tag_cloud', $tag_cloud, 60*60*12 );
}
echo $tag_cloud;

快取自定義查詢：

<?php

if ( false === ( $special_query_results = get_transient( 'special_query_results' ) ) ) {
    // It wasn't there, so regenerate the data and save the transient
     $special_query_results = new WP_Query( 'cat=5&order=random&tag=tech&post_meta_key=thumbnail' );
     set_transient( 'special_query_results', $special_query_results );
}

?>