引导单选按钮组选择的空/空返回值

Would appreciate someone explaining to me why I only get an empty string back from PHP when trying to get radio-button group selection.

$currentlyemployed = null;
if (isset($currentlyemployedyes)) {
  $currentlyemployed = "Yes";
}
else {
  $currentlyemployed = "No";
}

NOTE: text inputs within the same form post and I can get their values.

Example snippets:

START FORM MARKUP

<div class="row">
<div class="col-sm-6 text-left">
   <h5>Are you currently employed?</h5>
      <div class="control-group">
         <div class="controls">
            <label>
               <input type="radio" id="currentlyemployedyes" name="currentlyemployed" value="yes" />Yes</label>
            <label>
               <input type="radio" id="currentlyemployedno" name="currentlyemployed" value="no" />No</label>
             <p class="help-block"></p>
          </div>
       </div>
    </div>
</div>

END FORM MARKUP

START PHP CODE SNIPPET

$currentlyemployed = $_POST['currentlyemployed']; RETURNS empty string

/* FYI
$currentlyemployedyes = $_POST['currentlyemployedyes']; RETURNS "Yes"
$currentlyemployedno = $_POST['currentlyemployedno']; RETURNS "No"
*/

END PHP CODE SNIPPET

The code you have written works as expected. You can check out the snippet below. Bootstrap or not it does not matter. The name="currentlyemployed" sent from the form to php server and then php binds it into $_POST associative global array.

 <?php 
    echo "<pre>";
      var_dump($_POST);
    echo "</pre>";

      echo "Currently Employed: ".$_POST['currentlyemployed'];

    ?>
    <hr>

    <div class="row">
    <div class="col-sm-6 text-left">
      <form method="POST">
         <h5>Are you currently employed?</h5>
            <div class="control-group">
               <div class="controls">
                  <label>
                     <input type="radio" id="currentlyemployedyes" name="currentlyemployed" value="yes" />Yes</label>
                  <label>
                     <input type="radio" id="currentlyemployedno" name="currentlyemployed" value="no" />No</label>
                   <p class="help-block"></p>
                </div>
             </div>

             <input type="submit">
        </form>
        </div>
    </div>

I don't consider this a legitimate "answer", but, rather, a "work-around".

Would like to provide attribution, but forget where I found this, might have even been here on stack overflow.

                <div class="row">
                    <div class="col-sm-6 text-left">
                        <h5>Are you currently employed?</h5>
                        <div class="control-group">
                            <div class="controls">
                                <label>
                                    <input type="radio" id="currentlyemployedyes" name="currentlyemployed" value="yes" **onclick="$('#currentlyemployed').val('Yes');"** />
                                    Yes</label>
                                <label>
                                    <input type="radio" id="currentlyemployedno" name="currentlyemployed" value="no" **onclick="$('#currentlyemployed').val('No');"** />
                                    No</label>
                                <p class="help-block"></p>
                            </div>
                            **<input name="currentlyemployed" id="currentlyemployed" type="hidden" value="" />**
                        </div>
                    </div>
                </div>