preg_replace换成preg_replace_callback解决方法

preg_replace换成preg_replace_callback
 function fetch_str($source){
        $source = $this->smarty_prefilter_preCompile($source);
        return preg_replace("/{([^\}\{\n]*)}/e", "\$this->select('\\1');", $source);
  }
------解决思路----------------------

return preg_replace_callback("/{([^\}\{\n]*)}/", 
    function($m) {
      return $this->select($m[1]);
    }, $source);