php字符串变量输出 - PHP / 开源资源

大家好 ：
  我用fck编辑器生产一段html代码如：
  尊敬的{{email}}您好！
  Thank you for visiting 51customimprint, We have successful change your password .
  这个是个字符串 我现在想将里面的{{email}}替换成{$email}
  但是替换成功之后总是输出
  尊敬的{$email}您好！
  Thank you for visiting 51customimprint, We have successful change your password .
不知道该如何处理 请大家多多指教 万分感谢！

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友情支持~up~up~up~!

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不是替换面 {$email}

是 $mail 这个值替换 {email} 这个东西

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{<? echo $email ?>}

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PHP code:
<?php
$email='youname@domain.com';
$username='yourname';

$str = '尊敬的{{username}}您好！Thank you for visiting 51customimprint, We have successful changed your password and sent to {{email}}.';

//這樣也行,更容易理解
$reg_str = preg_replace("/\{\{(.+?)\}\}/e","\$\$1",$str);
echo $reg_str;
?>

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从上例
$reg_str = preg_replace("/\{{2}(\w+)\}{2}/e","$$1",$str);