Parse error: syntax error, unexpected T_STRING in V:\home\localhost\www\premium_urok\practice.php on line 4

<?php

session_start()
define ("FN", "gb.txt" );

if($_POST['submit']) {
     $name = trim(htmlspecialchars($_POST['name']));
	 $txt =  trim(htmlspecialchars($_POST['txt']));
	 $str = $name.':'.$txt.;
	 
	 if(file_put_contents(FN, $str, FILE_APPEND)) {
	     $_SESSION['res'] = 'Добавлено!';
		 header("Location: practice.php");
		 exit;
	 
	 }
     
	 
}

echo $_SESSION['res'];
unset($_SESSION['res']);
session_destroy();


?>
<form method="post">
    Имя*: <br /> 
    <input type="text"	name="name" /><br />
	Сообщение*: <br />
	<textarea name="txt" cols="30" rows="5"></textarea><br />
	<input type="submit" name="submit" value="Добавить" />
</form>	

Подскажите в чём тут ошибка