Доброго времени суток!
На PHP пишу меньше 2 недель, пишу небольшой проект. Столкнулся с проблемой, в одном из модулей выдается ошибка:
Warning: Cannot modify header information - headers already sent by (output started at C:\test\xampp\htdocs\v2\modules\mod_supplier\mod_supplier_edit.php:86) in C:\test\xampp\htdocs\v2\modules\mod_supplier\mod_supplier_edit.php on line 128

Аналогичные модули работают, погуглил тему, подходящего решения не нашел. Подскажите пожалуйста в чем проблема. Код модуля:

<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<?php
//Если пользователь не автаризован, то переход к авторизации
if (($_SESSION['authorized'] != 1) && ($_SESSION['admin'] != 1)) 
{
	header("Location:". HOMEPAGE);
	exit;
}
$supplier_id = null;
if (isset($_GET['id']))
	$supplier_id = $_GET['id'];
if (isset($supplier_id))
	$results = supplier::getById($supplier_id);
?>
<form action = "" method = "post" name = "supplier_edit" id = "form_edit" >
	<table>
		<?php
		if ($_SESSION['admin'] == 1)
		{
			switch ($_GET['supplier_reg'])
			{
				case "edit":
					$txt_supplier_id = (int)$results->supplier_id;
					$txt_supplier_name = htmlspecialchars($results->supplier_name);
					$txt_supplier_contr_name = htmlspecialchars($results->supplier_contr_name);
					$txt_user_id = (int)$results->user_id;
					$txt_supplier_man = htmlspecialchars($results->supplier_man);
					$txt_supplier_tel = htmlspecialchars($results->supplier_tel);
					$txt_supplier_j_address= htmlspecialchars($results->supplier_j_address);
					$txt_supplier_p_address= htmlspecialchars($results->supplier_p_address);
					break;
				case "add":
					$txt_supplier_id = !empty($_POST['supplier_id']) ? $_POST['supplier_id'] : "";
					$txt_supplier_name = !empty($_POST['supplier_name']) ? $_POST['supplier_name'] : "";
					$txt_supplier_contr_name = !empty($_POST['supplier_contr_name']) ? $_POST['supplier_contr_name'] : "";
					$txt_user_id = !empty($_POST['user_id']) ? $_POST['user_id'] : "";
					$txt_supplier_man = !empty($_POST['supplier_man']) ? $_POST['supplier_man'] : "";
					$txt_supplier_tel = !empty($_POST['supplier_tel']) ? $_POST['supplier_tel'] : "";
					$txt_supplier_j_address= !empty($_POST['supplier_j_address']) ? $_POST['supplier_j_address'] : "";
					$txt_supplier_p_address= !empty($_POST['supplier_p_address']) ? $_POST['supplier_p_address'] : "";
					break;
			}
			echo "
			<tr>
				<td><label for=\"txt_supplier_id\">id</label></td>
				<td><input type=\"text\" name=\"supplier_id\" class\"inputbox\" alt=\"user_id_\" size=\"50\" value=\"". $txt_supplier_id  ."\"/></td>
			</tr>
			<tr>
				<td><label for=\"user_login\">Поставщик</label></td>
				<td><input type=\"text\" name=\"supplier_name\" class\"inputbox\" alt=\"user_login_\" size=\"50\" value=\"". $txt_supplier_name ."\"/></td>
			</tr>
			<tr>
				<td><label for=\"txt_supplier_contr_name\">Название в договоре</label></td>
				<td><input type=\"text\" name=\"supplier_contr_name\" class=\"inputbox\" alt=\"user_name_\" size=\"50\" value=\"". $txt_supplier_contr_name ."\"/></td>
			</tr>
			<tr>
				<td><label for=\"user_id\">Менеджер</label></td>
				<td><select name=\"user_id\" size=\"1\">";
			$manager_list = user::getManagers();
			foreach ($manager_list['results'] as $val)
			{
				if ((int)$val->user_id == (int)$txt_user_id)
					$selected = "selected = \"selected\"";
				else
					$selected = "";
				echo "<option value = \"". $val->user_id ."\" ". $selected .">". $val->user_name ."</option>";
			}
			echo "
				</select></td>
			</tr>
			<tr>
				<td><label for=\"supplier_man\">Контактное лицо</label></td>
				<td><input type=\"text\" name=\"supplier_man\" class=\"inputbox\" alt=\"user_tel_\" size=\"50\" value=\"". $txt_supplier_man ."\"/></td>
			</tr>
			<tr>
				<td><label for=\"supplier_tel\">Телефон</label></td>
				<td><input type=\"text\" name=\"supplier_tel\" class=\"inputbox\" alt=\"user_mail_\" size=\"50\" value=\"". $txt_supplier_tel ."\"/></td>
			</tr>
			<tr>
				<td><label for=\"supplier_j_address\">Юридический адрес</label></td>
				<td><input type=\"text\" name=\"supplier_j_address\" class=\"inputbox\" alt=\"user_edit_\" size=\"50\" value=\"". $txt_supplier_j_address ."\"/></td>
			</tr>
			<tr>
				<td><label for=\"supplier_p_address\">Почтовый/Физический адрес</label></td>
				<td><input type=\"text\" name=\"supplier_p_address\" class=\"inputbox\" alt=\"user_edit_\" size=\"50\" value=\"". $txt_supplier_p_address ."\"/></td>
			</tr>";
		}
		?>
		<tr>
			<td></td>
			<td align = "right"><br><input type = "submit" name = "send" class = "button" value = "Сохранить" /></td>
		</tr>
	</table>
</form>
<?php
	if (!empty($_POST['send']))
	{
		if ((!empty($_POST['supplier_id'])) && (!empty($_POST['supplier_name'])) && (!empty($_POST['supplier_contr_name'])) && (!empty($_POST['supplier_man'])) && (!empty($_POST['supplier_tel'])) && (!empty($_POST['supplier_j_address'])) && (!empty($_POST['supplier_p_address'])))
		{
			$err = 0;
			switch ($_GET['supplier_reg'])
			{
				case "edit":
					$id_change = supplier::changeId($supplier_id, $_POST['supplier_id']);
					$results->supplier_id = (int)$_POST['supplier_id'];
					$results->supplier_name = $_POST['supplier_name'];
					$results->supplier_contr_name = $_POST['supplier_contr_name'];
					$results->user_id = (int)$_POST['user_id'];
					$results->supplier_man = $_POST['supplier_man'];
					$results->supplier_tel = $_POST['supplier_tel'];
					$results->supplier_j_address = $_POST['supplier_j_address'];
					$results->supplier_p_address = $_POST['supplier_p_address'];
					$results->update();
					break;
				case "add":
					$new_supplier = new supplier($_POST);
					$new_supplier->insert();
					break;
			}
		}
		else
		{
			$err = 1;
			echo "<p class=\"error\">Ошибка ввода данных!</p>";
		}
		if ($err == 0)
		{
			header("Location:./?page=modules/mod_supplier/mod_suppliers.php");
			exit;
		}
	}
?>