title: HTML Multiple Select value as comma separated string in GET variable
body: <p>I have set up a multi-select list as follows:</p>
  
  <pre><code>&lt;select id="cuisine-select" name="_sft_post_tag" multiple="multiple" tabindex="-1" class="select2-hidden-accessible" aria-hidden="true"&gt;
      &lt;option value="banting"&gt;Banting&lt;/option&gt;
      &lt;option value="pasta"&gt;Pasta&lt;/option&gt;
      &lt;option value="pizza"&gt;Pizza&lt;/option&gt;
      &lt;option value="seafood"&gt;Seafood&lt;/option&gt;
      &lt;option value="vegan"&gt;Vegan&lt;/option&gt;
      &lt;option value="vegetarian"&gt;Vegetarian&lt;/option&gt;
  &lt;/select&gt;
  </code></pre>
  
  <p>This allows the user to select multiple cuisines for their search.</p>
  
  <p>When the form is submitted, the URL sets multiple GET variables of the same name each with one of the selected values, like so:</p>
  
  <pre><code>/restaurant/?_sft_category=saturday&amp;_sft_post_tag=pizza&amp;_sft_post_tag=seafood
  </code></pre>
  
  <p>I require this to pre-select tag options on the results page. </p>
  
  <p>Where I am currently stuck is the structure of the URL. I require the URL to look as follows:</p>
  
  <pre><code>/restaurant/?_sft_category=saturday&amp;_sft_post_tag=pizza,seafood
  </code></pre>
  
  <p>In other words, I require <strong>one</strong> GET variable namely <strong>_sft_post_tag</strong> and all selected options must appear in a comma separated string. </p>
  
  <p>The Search form is part of a Wordpress plugin called Search &amp; Filter Pro and uses comma separated strings to pre-select options. The search form from the homepage uses the Select2 plugin.</p>
  
  <p>I have tried using <code>name="_sft_post_tag[]"</code> and then imploding the array into a comma separated string like so <code>implode(",", $_GET['_sft_post_tag'])</code>.</p>
  
  <p>This also didn't work. At the moment it'll only pre-populate the last value of the <code>_sft_post_tag</code></p>