fetch() — 取得输出内容
string fetch(string template,
             string cache_id,
             string compile_id);
  该函数将取得一个模板输出的内容,而不是显示出来。
  该函数需要指定一个合法的模板资源的类型和路径。
   第二个可选的参数$cache_id设置缓存,详情参见
   缓存。
  
 As an optional third parameter, you can pass a
 $compile_id.
 This is in the event that you want to compile different versions of
 the same template, such as having separate templates compiled
 for different languages. You can
 also set the 
 $compile_id variable once instead of passing
  this to each call to this function.
Example 14.21. fetch()
<?php
include('Smarty.class.php');
$smarty = new Smarty;
$smarty->setCaching(true);
// 按照URL来MD5生成一个特定的缓存ID
$cache_id = md5($_SERVER['REQUEST_URI']);
// 捕获输出
$output = $smarty->fetch('index.tpl', $cache_id);
// 处理输出的内容
echo $output;
?>
    
  
Example 14.22. 用fetch()来发邮件
     email_body.tpl模板的内容:
    
Dear {$contact_info.name},
Welcome and thank you for signing up as a member of our user group.
Click on the link below to login with your user name
of '{$contact_info.username}' so you can post in our forums.
{$login_url}
List master
{textformat wrap=40}
This is some long-winded disclaimer text that would automatically get wrapped
at 40 characters. This helps make the text easier to read in mail programs that
do not wrap sentences for you.
{/textformat}
    
	该PHP脚本使用了PHP的
     mail()函数。
    
<?php
// 从数据库或其他来源获取到$contact_info
$smarty->assign('contact_info',$contact_info);
$smarty->assign('login_url',"http://{$_SERVER['SERVER_NAME']}/login");
mail($contact_info['email'], 'Thank You', $smarty->fetch('email_body.tpl'));
?>
    
  
   参见
   {fetch}
   display(),
   {eval},
   和
   templateExists().