think\Template::parseLayout PHP Method

    private function parseLayout(&$content)
    {
        // 读取模板中的布局标签
        if (preg_match($this->getRegex('layout'), $content, $matches)) {
            // 替换Layout标签
            $content = str_replace($matches[0], '', $content);
            // 解析Layout标签
            $array = $this->parseAttr($matches[0]);
            if (!$this->config['layout_on'] || $this->config['layout_name'] != $array['name']) {
                // 读取布局模板
                $layoutFile = $this->parseTemplateFile($array['name']);
                if ($layoutFile) {
                    $replace = isset($array['replace']) ? $array['replace'] : $this->config['layout_item'];
                    // 替换布局的主体内容
                    $content = str_replace($replace, $content, file_get_contents($layoutFile));
                }
            }
        } else {
            $content = str_replace('{__NOLAYOUT__}', '', $content);
        }
        return;
    }