php多行字符串输出

$content_header =<<<CONTENT_HEADER
            <section class="content-header">
                <h1>
                    $this->page_title
                </h1>
                <ol class="breadcrumb">
                    <li><a href="__SITE__"><i class="fa fa-dashboard"></i> 首页</a></li>
                    $breadcrumb
                </ol>
            </section>    
CONTENT_HEADER;