使用php定义给出PW_SALT错误

i am making a token in which i am using PW_SALT for that when i am using define(PW_SALT,'(+3%_'); then its giving me error when i alert use of undefined constant PW_SALT. Don't know why this happening , m i missing something?

define(PW_SALT,'(+3%_');
$row=mysql_fetch_array($sql);
$uid=$row['uid'];
$expFormat = mktime(date("H"), date("i"), date("s"), date("m")  , date("d")+3, date("Y"));  
$expDate = date("Y-m-d H:i:s",$expFormat);  
echo $key = md5($uid . '_' . $email . rand(0,10000) .$expDate . PW_SALT);

The correct syntax is:

define('PW_SALT','(+3%_');

with quotes around the constant name. Check the documentation.