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list top parent category of post and parent's subcategories

<?php
/**
 * list of post's top parent category as a h3 and all subcategories of it, 
 * current post's category highlighted with a class
 */

function list_subcategories () {                                                                             
    $hide_empty = 0;                                                                                                       
    $current_class = 'current_item';                                                                                       
    global $post;

    //id of the current post
    $this_post_ID = $post->ID;                                                                                             
    
    //categories list of curent post
    $categories = get_the_category($post->ID);                                                                             
    
    //first category, parent category of current post
    $category_id = $categories[0]->cat_ID;

    // if it's not root category (0) then do
    if ($category_id) {
        
        // get alphabetical list of parent categories separated with ","
        $parentCatList = get_category_parents( $category_id, false, ",");
        
        // get first category slug of that list...
        $topParentSlug = substr( $parentCatList, 0, strpos($parentCatList, ',') );                                              
        
        // get the object of that slug
        $topParent = get_term_by( 'slug', $topParentSlug, 'category' );
        
        // get the id of that object 
        $ancestor = $topParent->term_id;
        
        // echo the name of the parent category
        echo "<h3>$topParent->name</h3>";

        //list of parent category's categories
        echo '<ul>';
        
            // making the array of subcategories objects
            $cat_array = get_categories( "echo=0&title_li=&depth=$levels&child_of=$ancestor&hide_empty=$hide_empty" );          

            foreach($cat_array as $category) { 
                
                // if the listed cat. is the current post's category, we set it as current
                if ( $category_id == $category->cat_ID ) { $is_current = "class='" .$current_class."'"; }                    
                
                // list the category with a link 
                echo '<li '. $is_current .'><a href="'.get_category_link( $category->term_id ).'">'. $category->name.'</a></li>';

            }
        echo "</ul>";
    }
}
?>
https://snipt.net/embed/c4e93f59109a4a34571448b8ed85838a/
/raw/c4e93f59109a4a34571448b8ed85838a/
c4e93f59109a4a34571448b8ed85838a
php
PHP
57
2019-07-24T00:14:51
True
False
False
/api/public/snipt/38174/
list-top-parent-category-of-post-and-parents-subcategories
<table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><a href="#L-1"> 1</a> <a href="#L-2"> 2</a> <a href="#L-3"> 3</a> <a href="#L-4"> 4</a> <a href="#L-5"> 5</a> <a href="#L-6"> 6</a> <a href="#L-7"> 7</a> <a href="#L-8"> 8</a> <a href="#L-9"> 9</a> <a href="#L-10">10</a> <a href="#L-11">11</a> <a href="#L-12">12</a> <a href="#L-13">13</a> <a href="#L-14">14</a> <a href="#L-15">15</a> <a href="#L-16">16</a> <a href="#L-17">17</a> <a href="#L-18">18</a> <a href="#L-19">19</a> <a href="#L-20">20</a> <a href="#L-21">21</a> <a href="#L-22">22</a> <a href="#L-23">23</a> <a href="#L-24">24</a> <a href="#L-25">25</a> <a href="#L-26">26</a> <a href="#L-27">27</a> <a href="#L-28">28</a> <a href="#L-29">29</a> <a href="#L-30">30</a> <a href="#L-31">31</a> <a href="#L-32">32</a> <a href="#L-33">33</a> <a href="#L-34">34</a> <a href="#L-35">35</a> <a href="#L-36">36</a> <a href="#L-37">37</a> <a href="#L-38">38</a> <a href="#L-39">39</a> <a href="#L-40">40</a> <a href="#L-41">41</a> <a href="#L-42">42</a> <a href="#L-43">43</a> <a href="#L-44">44</a> <a href="#L-45">45</a> <a href="#L-46">46</a> <a href="#L-47">47</a> <a href="#L-48">48</a> <a href="#L-49">49</a> <a href="#L-50">50</a> <a href="#L-51">51</a> <a href="#L-52">52</a> <a href="#L-53">53</a> <a href="#L-54">54</a> <a href="#L-55">55</a> <a href="#L-56">56</a> <a href="#L-57">57</a></pre></div></td><td class="code"><div class="highlight"><pre><span></span><span id="L-1"><a name="L-1"></a><span class="cp">&lt;?php</span> </span><span id="L-2"><a name="L-2"></a><span class="sd">/**</span> </span><span id="L-3"><a name="L-3"></a><span class="sd"> * list of post&#39;s top parent category as a h3 and all subcategories of it, </span> </span><span id="L-4"><a name="L-4"></a><span class="sd"> * current post&#39;s category highlighted with a class</span> </span><span id="L-5"><a name="L-5"></a><span class="sd"> */</span> </span><span id="L-6"><a name="L-6"></a> </span><span id="L-7"><a name="L-7"></a><span class="k">function</span> <span class="nf">list_subcategories</span> <span class="p">()</span> <span class="p">{</span> </span><span id="L-8"><a name="L-8"></a> <span class="nv">$hide_empty</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> </span><span id="L-9"><a name="L-9"></a> <span class="nv">$current_class</span> <span class="o">=</span> <span class="s1">&#39;current_item&#39;</span><span class="p">;</span> </span><span id="L-10"><a name="L-10"></a> <span class="k">global</span> <span class="nv">$post</span><span class="p">;</span> </span><span id="L-11"><a name="L-11"></a> </span><span id="L-12"><a name="L-12"></a> <span class="c1">//id of the current post</span> </span><span id="L-13"><a name="L-13"></a> <span class="nv">$this_post_ID</span> <span class="o">=</span> <span class="nv">$post</span><span class="o">-&gt;</span><span class="na">ID</span><span class="p">;</span> </span><span id="L-14"><a name="L-14"></a> </span><span id="L-15"><a name="L-15"></a> <span class="c1">//categories list of curent post</span> </span><span id="L-16"><a name="L-16"></a> <span class="nv">$categories</span> <span class="o">=</span> <span class="nx">get_the_category</span><span class="p">(</span><span class="nv">$post</span><span class="o">-&gt;</span><span class="na">ID</span><span class="p">);</span> </span><span id="L-17"><a name="L-17"></a> </span><span id="L-18"><a name="L-18"></a> <span class="c1">//first category, parent category of current post</span> </span><span id="L-19"><a name="L-19"></a> <span class="nv">$category_id</span> <span class="o">=</span> <span class="nv">$categories</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="o">-&gt;</span><span class="na">cat_ID</span><span class="p">;</span> </span><span id="L-20"><a name="L-20"></a> </span><span id="L-21"><a name="L-21"></a> <span class="c1">// if it&#39;s not root category (0) then do</span> </span><span id="L-22"><a name="L-22"></a> <span class="k">if</span> <span class="p">(</span><span class="nv">$category_id</span><span class="p">)</span> <span class="p">{</span> </span><span id="L-23"><a name="L-23"></a> </span><span id="L-24"><a name="L-24"></a> <span class="c1">// get alphabetical list of parent categories separated with &quot;,&quot;</span> </span><span id="L-25"><a name="L-25"></a> <span class="nv">$parentCatList</span> <span class="o">=</span> <span class="nx">get_category_parents</span><span class="p">(</span> <span class="nv">$category_id</span><span class="p">,</span> <span class="k">false</span><span class="p">,</span> <span class="s2">&quot;,&quot;</span><span class="p">);</span> </span><span id="L-26"><a name="L-26"></a> </span><span id="L-27"><a name="L-27"></a> <span class="c1">// get first category slug of that list...</span> </span><span id="L-28"><a name="L-28"></a> <span class="nv">$topParentSlug</span> <span class="o">=</span> <span class="nb">substr</span><span class="p">(</span> <span class="nv">$parentCatList</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="nb">strpos</span><span class="p">(</span><span class="nv">$parentCatList</span><span class="p">,</span> <span class="s1">&#39;,&#39;</span><span class="p">)</span> <span class="p">);</span> </span><span id="L-29"><a name="L-29"></a> </span><span id="L-30"><a name="L-30"></a> <span class="c1">// get the object of that slug</span> </span><span id="L-31"><a name="L-31"></a> <span class="nv">$topParent</span> <span class="o">=</span> <span class="nx">get_term_by</span><span class="p">(</span> <span class="s1">&#39;slug&#39;</span><span class="p">,</span> <span class="nv">$topParentSlug</span><span class="p">,</span> <span class="s1">&#39;category&#39;</span> <span class="p">);</span> </span><span id="L-32"><a name="L-32"></a> </span><span id="L-33"><a name="L-33"></a> <span class="c1">// get the id of that object </span> </span><span id="L-34"><a name="L-34"></a> <span class="nv">$ancestor</span> <span class="o">=</span> <span class="nv">$topParent</span><span class="o">-&gt;</span><span class="na">term_id</span><span class="p">;</span> </span><span id="L-35"><a name="L-35"></a> </span><span id="L-36"><a name="L-36"></a> <span class="c1">// echo the name of the parent category</span> </span><span id="L-37"><a name="L-37"></a> <span class="k">echo</span> <span class="s2">&quot;&lt;h3&gt;</span><span class="si">$topParent-&gt;name</span><span class="s2">&lt;/h3&gt;&quot;</span><span class="p">;</span> </span><span id="L-38"><a name="L-38"></a> </span><span id="L-39"><a name="L-39"></a> <span class="c1">//list of parent category&#39;s categories</span> </span><span id="L-40"><a name="L-40"></a> <span class="k">echo</span> <span class="s1">&#39;&lt;ul&gt;&#39;</span><span class="p">;</span> </span><span id="L-41"><a name="L-41"></a> </span><span id="L-42"><a name="L-42"></a> <span class="c1">// making the array of subcategories objects</span> </span><span id="L-43"><a name="L-43"></a> <span class="nv">$cat_array</span> <span class="o">=</span> <span class="nx">get_categories</span><span class="p">(</span> <span class="s2">&quot;echo=0&amp;title_li=&amp;depth=</span><span class="si">$levels</span><span class="s2">&amp;child_of=</span><span class="si">$ancestor</span><span class="s2">&amp;hide_empty=</span><span class="si">$hide_empty</span><span class="s2">&quot;</span> <span class="p">);</span> </span><span id="L-44"><a name="L-44"></a> </span><span id="L-45"><a name="L-45"></a> <span class="k">foreach</span><span class="p">(</span><span class="nv">$cat_array</span> <span class="k">as</span> <span class="nv">$category</span><span class="p">)</span> <span class="p">{</span> </span><span id="L-46"><a name="L-46"></a> </span><span id="L-47"><a name="L-47"></a> <span class="c1">// if the listed cat. is the current post&#39;s category, we set it as current</span> </span><span id="L-48"><a name="L-48"></a> <span class="k">if</span> <span class="p">(</span> <span class="nv">$category_id</span> <span class="o">==</span> <span class="nv">$category</span><span class="o">-&gt;</span><span class="na">cat_ID</span> <span class="p">)</span> <span class="p">{</span> <span class="nv">$is_current</span> <span class="o">=</span> <span class="s2">&quot;class=&#39;&quot;</span> <span class="o">.</span><span class="nv">$current_class</span><span class="o">.</span><span class="s2">&quot;&#39;&quot;</span><span class="p">;</span> <span class="p">}</span> </span><span id="L-49"><a name="L-49"></a> </span><span id="L-50"><a name="L-50"></a> <span class="c1">// list the category with a link </span> </span><span id="L-51"><a name="L-51"></a> <span class="k">echo</span> <span class="s1">&#39;&lt;li &#39;</span><span class="o">.</span> <span class="nv">$is_current</span> <span class="o">.</span><span class="s1">&#39;&gt;&lt;a href=&quot;&#39;</span><span class="o">.</span><span class="nx">get_category_link</span><span class="p">(</span> <span class="nv">$category</span><span class="o">-&gt;</span><span class="na">term_id</span> <span class="p">)</span><span class="o">.</span><span class="s1">&#39;&quot;&gt;&#39;</span><span class="o">.</span> <span class="nv">$category</span><span class="o">-&gt;</span><span class="na">name</span><span class="o">.</span><span class="s1">&#39;&lt;/a&gt;&lt;/li&gt;&#39;</span><span class="p">;</span> </span><span id="L-52"><a name="L-52"></a> </span><span id="L-53"><a name="L-53"></a> <span class="p">}</span> </span><span id="L-54"><a name="L-54"></a> <span class="k">echo</span> <span class="s2">&quot;&lt;/ul&gt;&quot;</span><span class="p">;</span> </span><span id="L-55"><a name="L-55"></a> <span class="p">}</span> </span><span id="L-56"><a name="L-56"></a><span class="p">}</span> </span><span id="L-57"><a name="L-57"></a><span class="cp">?&gt;</span><span class="x"></span> </span></pre></div> </td></tr></table>
categories, category, php, wordpress