สอบถามการ ใช้ ฟังก์ชั่น AES_ENCRYPT(); AES_DECRYPT(); ใน sql หน่อยครับ

<?
	$sql = "insert into user set staff_picture = aes_encrypt('abcd', '1234')";
	$query = mysql_query($sql);
	
	$sql = "select aes_decrypt(staff_picture, '1234') from user";
	$query = mysql_query($sql);
	while($rs = mysql_fetch_assoc($query)){
?>
		<p><?=$rs["aes_decrypt(staff_picture, '1234')"];?></p>
<?		
	}
?>

<?
	$sql = "insert into user set staff_picture = aes_encrypt('abcd', '1234')";
	$query = mysql_query($sql);
	
	$sql = "select aes_decrypt(staff_picture, '1234') from user";
	$query = mysql_query($sql);
	$rs = mysql_fetch_assoc($query);

	echo "<pre>";
	print_r ($rs);
	echo "</pre>";
?>