Obtaining Date as string from bootstrap-datetimepicker

Question

I'm using bootstrap and jquery to make a form that searches a database using a php file, I managed to add filters without issue, my problem is that now I've added a Date Picker using Bootstrap-DateTimePicker, while there is no problem with the displaying of the date in the form, I cannot seem to be able to get the actual string of the date as a variable into my php file.

This is the Form HTML right now:

<form id="buscarInv" action="index.php" method="post" class="navbar-form pull-left" role="search">
          <div class="form-group">
            <div class="input-group-btn search-panel">
                <button type="button" class="btn btn-default dropdown-toggle" data-toggle="dropdown">
                  <span id="search_concept">Filtrar</span> <span class="caret"></span>
                </button>
                <ul class="dropdown-menu" id="search-filter" role="menu">
                  <?php print("$salida");?>
                </ul>
                <input type="hidden" name="search_param" value="" id="search_param">         
                <input type="text" class="form-control" name="searchinv" placeholder="Buscar" onkeydown="searchq();">
            </div>
        </div>
        <div class='input-group date' name='datetimepicker1' id='datetimepicker1'>
              <span class="input-group-addon">
                <span class="glyphicon glyphicon-calendar"></span> Date
              </span>
            <input type='text' data-date-format="YYYY-MM-DD" class="form-control" placeholder="Fecha" name="fechaC" id="fechaC">
        </div>
     </form>

And here's the DateTimePicker script and the script to send the inputs to the php file. DateTimePicker:

$(function () {
            $('#datetimepicker1').datetimepicker({format: 'YYYY-MM-DD'});

        });

Search:

function searchq(){
  var searchTxt = $("input[name='searchinv']").val();
  var filter = $("input[name='search_param']").val();
  var fechaEnv = $("input[name='fechaC']").val();
   $.post("search.php",{searchVal: searchTxt, filter:filter, fechaEnv:fechaEnv}, function(output){
    $("#output").html(output);
  });
}

I've tried using name='datetimepicker1', tried to set the value of fechaC in the datetimepicker function, but nothing appears to work, am I missing something?

UPDATE: Added the PHP

 $output='<thead>
            <tr>
              <th>Producto</th>
              <th>Cantidad</th>
              <th>Precio</th>
              <th>Locacion</th>
              <th>Fecha</th>
            </tr>
          </thead>
          <tbody>';
$idcat='';
$fechaT = date('Y-m-d');
if(isset($_POST['searchVal'])){
  $searchq = $_POST['searchVal'];
  if(isset($_POST['fechaEnv'])){
      $fechaT = $fechaEnv;
      $output .= '<tr><td>Date should be displayed here: '.$fechaEnv.'</td></tr>';
    }

Yet when I echo the output it shows up as: "Date should be displayed here:" without adding the date

Answer 1

Forgot collect fechaEnv like $_POST, $fechaEnv= $_POST['fechaEnv']; .

 if(isset($_POST['fechaEnv'])){
      //$fechaT = $fechaEnv;
      $fechaEnv= $_POST['fechaEnv']; 
      $output .= '<tr><td>Date should be displayed here: '.$fechaEnv.'</td></tr>';
    }