PHP，变量里带有变量

//模拟从数据库中读出的数据<br />
$mcontent =<<< 'TXT'<br />
dear：{$user['username']}<br />
   你购买的商品：{$goods_name}，订单号{$goods_no}已下单成功，由于此商品近期销售火爆，请及时付款！<br />
TXT;<br />
<br />
//涉及的变量需自行保证存在<br />
$user['username'] = 'body';<br />
$goods_name = 'xxx';<br />
$goods_no = '123';<br />
<br />
//方案一 不过有不少人恐惧 eval<br />
$mcontent = eval("return \"$mcontent\";");<br />
echo $mcontent;<br />
<br />
//方案二 动态创建函数，格式有点绕人<br />
$f = create_function('$user,$goods_name,$goods_no', "return \"$mcontent\";");<br />
$mcontent = $f($user, $goods_name, $goods_no);<br />
echo $mcontent;<br />
//或<br />
$f = create_function('$user,$goods_name,$goods_no', 'return "' . $mcontent . '";');<br />
$mcontent = $f($user, $goods_name, $goods_no);<br />
echo $mcontent;<br />
<br />
//方案三 模板变量替换，这是解释型模板引擎的做法<br />
$mcontent = preg_replace('/{\$[^}]+}/e', '$1', $mcontent);<br />
echo $mcontent;<br />