Dynamically generated inputs where not submitted - php

Question

I have a form which is a bunch of elements. Plus there is a Button that creates Input-Elements dynamically:
$(document).ready(function() {
var counter = 0;
$("#addNewItem").on("click", function() {
counter++;
// The PHP handle to create the elements
$.get('showItem.php?zahl=' + counter ,function(data) {
// Add Items:
$('#newItems').after(data);
//Button zum erzeugen Enablen:
$( "#btn_createItem" ).removeAttr( "disabled" );
})
});
});
The PHP-handle contains this:
<div class="row" style="margin-bottom: 1em;" id="item<? echo $zahl; ?>" >
<div class="col-md-6">
<div class="form-group">
<label for="taskForUser"> Product:</label>
<select class="form-control select2" style="width: 100%;" name="prItem<? echo $zahl; ?>" id="prItem<? echo $zahl; ?>">
<option selected>Please choose...</option>
<? //foreach($stmtPL as $rowPL) {
while($rowPRL = $stmtPRL->fetch(PDO::FETCH_NUM)) {
// Get List from Database: ?>
<option><? echo $rowPRL[1] . " * " . $rowPRL[2] . " * " . $rowPRL[4]; ?></option>
<? } ?>
</select>
</div>
</div>
<div class="col-md-3">
<div class="form-group">
<label for="name">Count:</label>
<input type="text" class="form-control" id="anzahl<? echo $zahl; ?>" name="anzahl<? echo $zahl; ?>" value="1" maxlength="5">
<div class="help-block with-errors"></div>
</div>
</div> <!-- /col -->
<div class="col-md-3">
<div class="form-group">
<label for="name"> </label><br />
</i>
</div>
</div><!-- /col -->
When I click on the button to submit the form, the dynamically generated fields are not present. I tested it with a simple: "print_r($_POST);"
Only the "hardcoded" fields are listet in the array. What can it be?