php缓冲 output_buffering的使用详解

　　 /*

　　* Buffer the output

　　*

　　* We buffer the output for two reasons:

　　* 1. Speed. You get a significant speed boost.

　　* 2. So that the final rendered template can be

　　* post-processed by the output class. Why do we

　　* need post processing? For one thing, in order to

　　* show the elapsed page load time. Unless we

　　* can intercept the content right before it's sent to

　　* the browser and then stop the timer it won't be accurate.

　　*/

　　ob_start();

　　// If the PHP installation does not support short tags we'll

　　// do a little string replacement, changing the short tags

　　// to standard PHP echo statements.

　　if ((bool) @ini_get('short_open_tag') === FALSE AND config_item('rewrite_short_tags') == TRUE)

　　{

　　//替换短标记<?=***>

　　echo eval('?>'.preg_replace("/;*s*?>/", "; ?>", str_replace('<?=', '<?php echo ', file_get_contents($_ci_path))));

　　}

　　else

　　{

　　include($_ci_path); // include() vs include_once() allows for multiple views with the same name

　　}

　　//记录调试信息

　　log_message('debug', 'File loaded: '.$_ci_path);

　　// Return the file data if requested

　　if ($_ci_return === TRUE)

　　{

　　$buffer = ob_get_contents();

　　@ob_end_clean();

　　return $buffer;

　　}

　　/*

　　* Flush the buffer... or buff the flusher?

　　*

　　* In order to permit views to be nested within

　　* other views, we need to flush the content back out whenever

　　* we are beyond the first level of output buffering so that

　　* it can be seen and included properly by the first included

　　* template and any subsequent ones. Oy!

　　*

　　*/

　　if (ob_get_level() > $this->_ci_ob_level + 1)

　　{

　　ob_end_flush();

　　}

　　else

　　{

　　//将模板内容添加到输出流中

　　$_ci_CI->output->append_output(ob_get_contents());

　　//清除buffer

　　@ob_end_clean();

　　}