我found this bit of very useful code产生下拉的URL查询字符串多个自定义分类使用。
下面的代码，在PHP中if(isset($_GET['taxonomies']))文件一堆if(empty($_GET['taxonomies']))和archive.php声明配对，排序的工作在跨越三个自定义分类筛选职位。
但是，如果URL查询参数是不是空的它才会起作用。例如：
example.com/custom-post-type-slug/?taxonomy1=term1&taxonomy2=termA&taxonomy3=termZ
...工作得很好。
example.com/custom-post-type-slug/?taxonomy1=term1&taxonomy2=termA
...也能正常工作。
然而，由代码创建的下拉下面将生成包括空查询参数，诸如URL的查询字符串：
example.com/custom-post-type-slug/?taxonomy1=term1&taxonomy2=&taxonomy3=termZ
分类学2空的查询参数打破它。由于做了所有的查询参数丢失：
example.com/custom-post-type-slug/?taxonomy1=&taxonomy2=&taxonomy3=
如何调整下面的代码删除URL查询参数，如果没有相应的价值？
最理想的情况是，如果没有URL查询值，查询参数从字符串中删除。我如何做，与此代码？
这是我functions.php文件。
function get_terms_dropdown_taxonomy1($taxonomies, $args){
$myterms = get_terms($taxonomies, $args);
$output ="<select name='taxonomy1'>";
$output .="<option value=''>All Taxonomy 1</option>";
foreach($myterms as $term){
$root_url = get_bloginfo('url');
$term_taxonomy=$term->taxonomy;
$term_slug=$term->slug;
$term_name =$term->name;
$link = $term_slug;
$output .="<option value='".$link."'>".$term_name."</option>";
}
$output .="</select>";
return $output;
}
function get_terms_dropdown_taxonomy2($taxonomies, $args){
$myterms = get_terms($taxonomies, $args);
$output ="<select name='taxonomy2'>";
$output .="<option value=''>All Taxonomy 2</option>";
foreach($myterms as $term){
$root_url = get_bloginfo('url');
$term_taxonomy=$term->taxonomy;
$term_slug=$term->slug;
$term_name =$term->name;
$link = $term_slug;
$output .="<option value='".$link."'>".$term_name."</option>";
}
$output .="</select>";
return $output;
}
function get_terms_dropdown_taxonomy3($taxonomies, $args){
$myterms = get_terms($taxonomies, $args);
$output ="<select name='taxonomy3'>";
$output .="<option value=''>All Taxonomy 3</option>";
foreach($myterms as $term){
$root_url = get_bloginfo('url');
$term_taxonomy=$term->taxonomy;
$term_slug=$term->slug;
$term_name =$term->name;
$link = $term_slug;
$output .="<option value='".$link."'>".$term_name."</option>";
}
$output .="</select>";
return $output;
}
同时，这是一个模板文件中的输出。
<?php
$taxonomies = array('taxonomy1');
$args = array('orderby'=>'name','hide_empty'=>1);
$select = get_terms_dropdown_taxonomy1($taxonomies, $args);
$select = preg_replace("#<select([^>]*)>#", "<select$1 id='taxonomy1' class='dropdown' aria-label='Select a taxonomy 1'>", $select);
echo $select;
?>
<?php
$taxonomies = array('taxonomy2');
$args = array('orderby'=>'name','hide_empty'=>1);
$select = get_terms_dropdown_taxonomy2($taxonomies, $args);
$select = preg_replace("#<select([^>]*)>#", "<select$1 id='taxonomy2' class='dropdown' aria-label='Select a taxonomy 2'>", $select);
echo $select;
?>
<?php
$taxonomies = array('taxonomy3');
$args = array('orderby'=>'name','hide_empty'=>1);
$select = get_terms_dropdown_taxonomy3($taxonomies, $args);
$select = preg_replace("#<select([^>]*)>#", "<select$1 id='taxonomy3' class='dropdown' aria-label='Select a taxonomy 3'>", $select);
echo $select;
?>
编辑：在这里感谢你的帮助是最后的工作代码。
<?php
$url = parse_url($_SERVER['REQUEST_URI']);
// WORKING | all taxonomy1, taxonomy2, and taxonomy3; no values for any taxonomy; displays six most recent posts
if(empty($_GET['taxonomy1']) && empty($_GET['taxonomy2']) && empty($_GET['taxonomy3'])) {
$paged = ( get_query_var( 'paged' ) ) ? absint( get_query_var( 'paged' ) ) : 1; $exec_query = new WP_Query( array (
'post_type' => 'custom_post_type',
'publish_status' => 'publish',
'posts_per_page' => 6,
'paged' => $paged,
) );
}
// WORKING | taxonomy1 only; no values for taxonomy2 or taxonomy3
elseif(empty($_GET['taxonomy2']) && empty($_GET['taxonomy3'])) {
$paged = ( get_query_var( 'paged' ) ) ? absint( get_query_var( 'paged' ) ) : 1; $exec_query = new WP_Query( array (
'post_type' => 'custom_post_type',
'publish_status' => 'publish',
'posts_per_page' => 6,
'paged' => $paged,
'tax_query' => array(
array(
'taxonomy' => 'taxonomy1',
'field' => 'slug',
'terms' => $_GET['taxonomy1'],
'operator' => 'IN',
),
),
) );
}
// WORKING | issue only; no values for taxonomy1 or taxonomy3; displays six most recent taxonomy2 posts
elseif(empty($_GET['taxonomy1']) && empty($_GET['taxonomy3'])) {
$paged = ( get_query_var( 'paged' ) ) ? absint( get_query_var( 'paged' ) ) : 1; $exec_query = new WP_Query( array (
'post_type' => 'custom_post_type',
'publish_status' => 'publish',
'posts_per_page' => 6,
'paged' => $paged,
'tax_query' => array(
array(
'taxonomy' => 'taxonomy2',
'field' => 'slug',
'terms' => $_GET['taxonomy2'],
'operator' => 'IN',
),
),
) );
}
// WORKING | taxonomy3 only; no values for taxonomy1 or taxonomy2
elseif(empty($_GET['taxonomy1']) && empty($_GET['taxonomy2'])) {
$paged = ( get_query_var( 'paged' ) ) ? absint( get_query_var( 'paged' ) ) : 1; $exec_query = new WP_Query( array (
'post_type' => 'custom_post_type',
'publish_status' => 'publish',
'posts_per_page' => 6,
'paged' => $paged,
'tax_query' => array(
array(
'taxonomy' => 'taxonomy3',
'field' => 'slug',
'terms' => $_GET['taxonomy3'],
'operator' => 'IN',
),
),
) );
}
// WORKING | taxonomy2 in taxonomy3; no values for taxonomy1
elseif(empty($_GET['taxonomy1'])) {
$paged = ( get_query_var( 'paged' ) ) ? absint( get_query_var( 'paged' ) ) : 1; $exec_query = new WP_Query( array (
'post_type' => 'custom_post_type',
'publish_status' => 'publish',
'posts_per_page' => 6,
'paged' => $paged,
'tax_query' => array(
'relation' => 'AND',
array(
'taxonomy' => 'taxonomy2',
'field' => 'slug',
'terms' => $_GET['taxonomy2'],
'operator' => 'IN',
),
array(
'taxonomy' => 'taxonomy3',
'field' => 'slug',
'terms' => $_GET['taxonomy3'],
'operator' => 'IN',
),
),
) );
}
// WORKING | taxonomy1 in taxonomy3; no values for taxonomy2
elseif(empty($_GET['taxonomy2'])) {
$paged = ( get_query_var( 'paged' ) ) ? absint( get_query_var( 'paged' ) ) : 1; $exec_query = new WP_Query( array (
'post_type' => 'custom_post_type',
'publish_status' => 'publish',
'posts_per_page' => 6,
'paged' => $paged,
'tax_query' => array(
'relation' => 'AND',
array(
'taxonomy' => 'taxonomy1',
'field' => 'slug',
'terms' => $_GET['taxonomy1'],
'operator' => 'IN',
),
array(
'taxonomy' => 'taxonomy3',
'field' => 'slug',
'terms' => $_GET['taxonomy3'],
'operator' => 'IN',
),
),
) );
}
// WORKING | taxonomy1 on taxonomy2; no values for taxonomy3
elseif(empty($_GET['taxonomy3'])) {
$paged = ( get_query_var( 'paged' ) ) ? absint( get_query_var( 'paged' ) ) : 1; $exec_query = new WP_Query( array (
'post_type' => 'custom_post_type',
'publish_status' => 'publish',
'posts_per_page' => 6,
'paged' => $paged,
'tax_query' => array(
'relation' => 'AND',
array(
'taxonomy' => 'taxonomy1',
'field' => 'slug',
'terms' => $_GET['taxonomy1'],
'operator' => 'IN',
),
array(
'taxonomy' => 'taxonomy2',
'field' => 'slug',
'terms' => $_GET['taxonomy2'],
'operator' => 'IN',
),
),
) );
}
elseif(isset($_GET['taxonomy1']) && ($_GET['taxonomy2']) && ($_GET['taxonomy3'])) {
$paged = ( get_query_var( 'paged' ) ) ? absint( get_query_var( 'paged' ) ) : 1; $exec_query = new WP_Query( array (
'post_type' => 'custom_post_type',
'publish_status' => 'publish',
'posts_per_page' => 6,
'paged' => $paged,
'tax_query' => array(
'relation' => 'AND',
array(
'taxonomy' => 'taxonomy1',
'field' => 'slug',
'terms' => $_GET['taxonomy1'],
'operator' => 'IN',
),
array(
'taxonomy' => 'taxonomy2',
'field' => 'slug',
'terms' => $_GET['taxonomy2'],
'operator' => 'IN',
),
array(
'taxonomy' => 'taxonomy3',
'field' => 'slug',
'terms' => $_GET['taxonomy3'],
'operator' => 'IN',
),
),
) );
}
else{
$paged = ( get_query_var( 'paged' ) ) ? absint( get_query_var( 'paged' ) ) : 1; $exec_query = new WP_Query( array (
'post_type' => 'custom_post_type',
'publish_status' => 'publish',
'posts_per_page' => 6,
'paged' => $paged,
) );
}
if ( $exec_query->have_posts() ) { ?><?php while ( $exec_query->have_posts() ): $exec_query->the_post(); ?>
如果你的查询参数存在isset()将返回true。这听起来像你的代码假设，如果参数存在，它也包含了一些有用的价值。这不是什么isset()检查。
在这种情况下，the empty() function可能是你在找什么。这将返回true如果一个变量不存在，或者如果它包含一个假的y值，如您得到一个空字符串。
更改您的if语句来if (!empty($_GET['taxonomies']))应该做的伎俩。
请记住，字符串"0"也被认为是假-Y，因此“空”，因此，如果这是一个有效的价值为你的查询参数之一，你将需要添加一个明确的检查了点。
为了说明@rickdenhaan说什么，这里有一些例子：
// Check if $variable is empty, using empty($variable)
$variable = ""; // true
$variable = " "; // false
$variable = 0; // true
$variable = 1; // false
$variable = null; // true
$variable = false; // true
// Check if $variable was defined, using isset($variable)
$variable = ""; // true
$variable = " "; // true
$variable = 0; // true
$variable = 1; // true
$variable = null; // false
$variable = false; // true
好奇心：如文档中所描述的，empty()功能实质上是：
(!isset($variable) || $variable == false)