数据库读出来的数据如何与定义好的常量对应

数据库读出来的数据怎么与定义好的常量对应？
consstant.php:
define("town_9","横沥");
define("town_10","桥头");
define("town_11","谢岗");
define("town_12","东坑");
define("town_13","常平");
define("town_14","寮步");
define("town_15","大朗");
define("town_16","黄江");

test.php:
...//数据库操作
echo $row[0];//$row[0]输出是town_14
?>

这样运行test.php显示出来是town_14,而输出定义好的常量寮步.这如何是好？
------解决方案--------------------

<br />define("town_9","横沥");<br />define("town_10","桥头");<br />define("town_11","谢岗");<br />define("town_12","东坑");<br />define("town_13","常平");<br />define("town_14","寮步");<br />define("town_15","大朗");<br />define("town_16","黄江");<br /><br />//数据库操作<br />$row = array();<br />$row[0] = "town_14";<br /><br />$defined_constants = get_defined_constants();<br />echo $defined_constants[$row[0]]; // 寮步<br />