<div class="form-group">
<label>Категория</label>
<?
$catt = mysql_query("SELECT * FROM `bb_catproduct` WHERE parent=0");
?>
<select name="cat" id="catOne" class="form-control" onchange="parent()">
<option value="">Выберите категорию</option>
<? while($cat = mysql_fetch_assoc($catt)){ ?>
<option value="<? echo $cat["id"]; ?>"><? echo $cat["name"]; ?></option>
<? } ?>
</select>
</div>
<div id="pr"></div>
<script type="text/javascript">
function parent(){
$.ajax({
type: "POST",
url: "ajax/ajaxCat.php",
data: "catParent="+$('#catOne').val(),
success: function(pr){
$('#pr').html(pr);
}
})
};
</script>