我整天都在黑客攻击一个自定义的帖子类型搜索/过滤系统。到目前为止，我有：

function kdev_property_query($query) {

if(isset($_POST[\'rooms_n\'])) $_SESSION[\'rooms_n\'] = $_POST[\'rooms_n\'];
if(isset($_POST[\'univer\'])) $_SESSION[\'univer\'] = $_POST[\'univer\'];
if(isset($_POST[\'area_t\'])) $_SESSION[\'area_t\'] = $_POST[\'area_t\'];

$query_post_type = $query->query_vars["post_type"];

if( !is_post_type_archive( \'properties\' ) || $query_post_type == \'nav_menu_item\' ) return;

//Show all available properties
$query->set(\'posts_per_page\',\'-1\');

$meta_query = array();
$tax_query = array();

global $query_string;
if(isset($_SESSION[\'rooms_n\'])) $room_query = $_SESSION[\'rooms_n\'];
if(isset($_SESSION[\'univer\'])) $uni_query = $_SESSION[\'univer\'];
if(isset($_SESSION[\'area_t\'])) $area_query = $_SESSION[\'area_t\'];

if(isset($room_query)) {
    $meta_query[] = array(
        \'key\' => \'_rooms\',
        \'value\' => $room_query
    );
}

if(isset($uni_query)) {
    $tax_query[] = array(
        \'taxonomy\' => \'university\',
        \'field\' => \'slug\',
        \'terms\' => $uni_query
    );
}

if(isset($area_query)) {
    $tax_query[] = array(
        \'taxonomy\' => \'area\',
        \'field\' => \'slug\',
        \'terms\' => $area_query
    );
}


if( ! empty( $meta_query ) )
        $query->set( \'meta_query\', $meta_query );
if( ! empty( $tax_query ) )
        $query->set( \'tax_query\', $tax_query );


}

add_action(\'pre_get_posts\', \'kdev_property_query\', 1);

我使用以下表单进行搜索：

function display_area_university_filter_form(){
?>
<div id="search-filters">
<form method="post" action="">
<h3 id="property-search"><span>property search</span></h3>

<?php
    if(isset($_SESSION[\'univer\'])) $uni = $_SESSION[\'univer\'];
    else if(is_tax( \'university\' ) ) $uni = get_query_var( \'term\' );
    if(isset($uni)) $uni = strtolower($uni);?>
<p><label for="univer">University:</label> <select name="univer"><option value="NULL">Any</option>
<?php 
    $uni_terms =  get_categories(\'taxonomy=university\'); 
    if (isset($uni)){
        foreach ($uni_terms as $term) {
            $option = \'<option value="\'.$term->slug.\'"\';
            if ($uni == $term->slug){
                $option.= \' selected="selected"\';
            }
            $option .= \'>\'.$term->name;
            $option .= \'</option>\';
            echo $option;
        }
    }else{
        foreach ($uni_terms as $term) {
            $option = \'<option value="\'.$term->slug.\'"\';
            $option .= \'>\'.$term->name;
            $option .= \'</option>\';
            echo $option;
        }
    }
?>
</select>
</p>
<input type="hidden" name="custom_filter" value="area_uni">

<p>

    <?php
    if(isset($_SESSION[\'area_t\'])) $area = $_SESSION[\'area_t\'];
    else if(is_tax( \'area\' ) ) $area = get_query_var( \'term\' );
    if(isset($area)) $area = strtolower($area);?>
    <label for="area_t">Area:</label> 

    <select name="area_t">
        <option value="NULL">Any</option>
    <?php 
        $area_terms =  get_categories(\'taxonomy=area\'); 
        if (isset($area)){
            foreach ($area_terms as $term) {
                $option = \'<option value="\'.$term->slug.\'"\';
                if ($area == $term->slug){
                    $option.= \' selected="selected"\';
                }
                $option .= \'>\'.$term->name;
                $option .= \'</option>\';
                echo $option;
            }
        }else{
            foreach ($area_terms as $term) {
                $option = \'<option value="\'.$term->slug.\'"\';
                $option .= \'>\'.$term->name;
                $option .= \'</option>\';
                echo $option;
            }
        }
    ?>
    </select>
</p>

<p>
<?php 
if(isset($_SESSION[\'rooms_n\'])) $rooms = $_SESSION[\'rooms_n\'];

?>
    <label for="rooms_n">Bedrooms:</label> 
    <select name="rooms_n">
        <option value="NULL">Any</option>
        <?php 
        $room_array = array(3,4,5,6,7);
        foreach($room_array as $no) {
        $output = \'<option \';
        if(isset($rooms) && $rooms == $no) $output .= \'selected="selected" \';
        $output .= \'value="\'.$no.\'">\'.$no.\'</option>\';
        echo $output;
        } ?>

    </select>
</p>


<p><input class="<?php if(is_archive()) echo \'new-search \'; ?>button" type="submit" name="search_props" value="<?php if(is_archive() || is_post_type_archive(\'properties\')) echo \'New \'; ?>Search"></p>

</form>
</div>
<?php

}

如果我同时搜索所有三个值（大学、面积和房间），页面将显示正确的结果。但是，如果任何或所有选项字段留空，则不会返回帖子。

$GLOBALS[\'wp\\u query\']->请求为所有选项均已选择返回：

SELECT   wp_posts.* FROM wp_posts  INNER JOIN wp_term_relationships ON (wp_posts.ID = wp_term_relationships.object_id) INNER JOIN wp_term_relationships AS tt1 ON (wp_posts.ID = tt1.object_id) INNER JOIN wp_postmeta ON (wp_posts.ID = wp_postmeta.post_id) WHERE 1=1  AND ( wp_term_relationships.term_taxonomy_id IN (5) AND tt1.term_taxonomy_id IN (18,15) ) AND wp_posts.post_type = \'properties\' AND (wp_posts.post_status = \'publish\' OR wp_posts.post_status = \'private\') AND ( (wp_postmeta.meta_key = \'_rooms\' AND CAST(wp_postmeta.meta_value AS CHAR) = \'4\') ) GROUP BY wp_posts.ID ORDER BY wp_posts.post_date DESC 

。。。如果仅选择了大学和房间选项：

 SELECT   wp_posts.* FROM wp_posts  INNER JOIN wp_postmeta ON (wp_posts.ID = wp_postmeta.post_id) WHERE 1=1  AND 0 = 1 AND wp_posts.post_type = \'properties\' AND (wp_posts.post_status = \'publish\' OR wp_posts.post_status = \'private\') AND ( (wp_postmeta.meta_key = \'_rooms\' AND CAST(wp_postmeta.meta_value AS CHAR) = \'4\') ) GROUP BY wp_posts.ID ORDER BY wp_posts.post_date DESC 

请帮忙！这简直要了我的命！如果您需要更多信息，请询问。

<option value="">Any</option>

!empty()