解决AJAX请求200状态但JSON解析错误：确保服务器端响应格式一致性

$.ajax({
    url : ajax_url,
    dataType: 'json', // 关键：期望服务器返回JSON
    contentType: "application/json",
    data : data,
    beforeSend : function ( e ) {
         e.setRequestHeader('Accept', 'application/json; charset=utf-8')
    },
    success : function(response) {
        // ... 处理JSON响应 ...
    },
    error: function(errorThrown){
        console.log(errorThrown); // 当发生parseError时，这里会捕获到
    }    
});

function my_ajax_filter_search_callback() {
    header("Content-Type: application/json"); // 声明返回JSON类型
    // ... 其他查询逻辑 ...

    if ( $search_query->have_posts() ) {
        // ... 构建结果数组 ...
        echo json_encode($result); // 正确：输出JSON数组
    } else {
        echo 'no posts found'; // 错误：这里输出的是纯文本字符串
    }
    wp_die();
}

function my_ajax_filter_search_callback() {
    header("Content-Type: application/json"); 

    $meta_query = array('relation' => 'AND');
    $search_query = null; // 初始化 $search_query

    if(isset($_GET['search'])) {
        $search = sanitize_text_field( $_GET['search'] );
        $search_query = new WP_Query( array(
            'post_type' => 'post',
            'posts_per_page' => -1,
            's' => $search
        ) );
    } else {
        // 如果没有搜索参数，可能需要根据 $args 来初始化，或者直接返回空
        // 为简化示例，这里假设没有搜索参数时也可能导致无结果
        $search_query = new WP_Query( $args ); // 假设 $args 已定义或为空
    }

    if ( $search_query && $search_query->have_posts() ) { // 确保 $search_query 已初始化
        $result = array();

        while ( $search_query->have_posts() ) {
            $search_query->the_post();
            $result[] = array(
                "id" => get_the_ID(),
                "title" => get_the_title(),
                "content" => get_the_content(),
                "permalink" => get_permalink(),
                "poster" => wp_get_attachment_url(get_post_thumbnail_id(get_the_ID()),'full')
            );
        }
        wp_reset_query();

        echo json_encode($result); // 有结果时返回JSON数组

    } else {
        echo json_encode([]); // 无结果时返回空JSON数组
    }
    wp_die();
}

// ...
} else {
    echo json_encode(array(
        'status' => 'no_results',
        'message' => 'No matching movies found. Try a different filter or search keyword'
    ));
}
wp_die();

success : function(response) {
    mafs.find("ul").empty();
    // 检查响应中是否存在特定的数据数组，或者检查状态信息
    if(response && response.status === 'no_results') { // 如果返回的是带有状态信息的对象
        var html  = "<p class='no-result'>No matching movies found. Try a different filter or search keyword</p>";
        mafs.find("ul").append(html);
    } else if (response && Array.isArray(response) && response.length > 0) { // 如果返回的是非空数组
        for(var i = 0 ;  i < response.length ; i++) {
            // ... 构建电影列表 ...
        }
    } else { // 如果返回空数组或者其他无法识别的空数据
        var html  = "<p class='no-result'>No matching movies found. Try a different filter or search keyword</p>";
        mafs.find("ul").append(html);
    }
},

success : function(response) {
    mafs.find("ul").empty();
    // 当PHP返回[]时，jQuery.isEmptyObject(response)为true
    if(!jQuery.isEmptyObject(response)){ // 此时 response 为非空数组
        for(var i = 0 ;  i < response.length ; i++) {
            var html  = "<li id='movie-" + response[i].id + "'>";
            html += "  <a href='" + response[i].permalink + "' title='" + response[i].title + "'>";
            html += "      <img src='" + response[i].poster + "' alt='" + response[i].title + "' />";
            html += "      <div class='movie-info'>";
            html += "          <h4>" + response[i].title + "</h4>";
            html += "          <p>" + response[i].content + "</p>";
            html += "      </div>";
            html += "  </a>";
            html += "</li>";
            mafs.find("ul").append(html);
        }
    } else { // 此时 response 为空数组 []
        var html  = "<p class='no-result'>No matching movies found. Try a different filter or search keyword</p>";
        mafs.find("ul").append(html);
    }
},