我們開始分析core/Output.php。
它負責產出最後結果，並傳送給使用者（瀏覽器）。
_zlib_oc = @ini_get('zlib.output_compression');
// Get mime types for later
if (defined('ENVIRONMENT') AND file_exists(APPPATH.'config/'.ENVIRONMENT.'/mimes.php'))
{
include APPPATH.'config/'.ENVIRONMENT.'/mimes.php';
}
else
{
include APPPATH.'config/mimes.php';
}
$this->mime_types = $mimes;
log_message('debug', "Output Class Initialized");
}
// --------------------------------------------------------------------
/**
* Get Output
*
* Returns the current output string
*
* @access public
* @return string
*/
function get_output()
{
return $this->final_output;
}
// --------------------------------------------------------------------
/**
* Set Output
*
* Sets the output string
*
* @access public
* @param string
* @return void
*/
function set_output($output)
{
$this->final_output = $output;
return $this;
}
這個set函數最後傳回 $this，這讓函數能夠串接起來使用。
在不需要回傳值的函數，常常可以這麼做。
// --------------------------------------------------------------------
/**
* Append Output
*
* Appends data onto the output string
*
* @access public
* @param string
* @return void
*/
function append_output($output)
{
if ($this->final_output == '')
{
$this->final_output = $output;
}
else
{
$this->final_output .= $output;
}
return $this;
}
注意這個將字串加進output的函數。
我認為if判斷式多餘了，直接 $this->final_output .= $output 即可。
// --------------------------------------------------------------------
/**
* Set Header
*
* Lets you set a server header which will be outputted with the final display.
*
* Note: If a file is cached, headers will not be sent. We need to figure out
* how to permit header data to be saved with the cache data...
*
* @access public
* @param string
* @param bool
* @return void
*/
function set_header($header, $replace = TRUE)
{
// If zlib.output_compression is enabled it will compress the output,
// but it will not modify the content-length header to compensate for
// the reduction, causing the browser to hang waiting for more data.
// We'll just skip content-length in those cases.
if ($this->_zlib_oc && strncasecmp($header, 'content-length', 14) == 0)
{
return;
}
$this->headers[] = array($header, $replace);
return $this;
}
本來我只知道，PHP的字串比較，用strcmp比==好。
看到這邊才知道，還有strncasecmp跟strncmp函數。
$header是字串、$replace是布林值，這邊卻將他們放進一個陣列，然後再塞進headers變數。
我個人很討厭這種將不同類型變數放進同一個陣列的作法：這代表讀這段code的人要先知道陣列內的順序有特殊意義、而不只是順序，否則將難以理解。
// --------------------------------------------------------------------
/**
* Set Content Type Header
*
* @access public
* @param string extension of the file we're outputting
* @return void
*/
function set_content_type($mime_type)
{
if (strpos($mime_type, '/') === FALSE)
{
$extension = ltrim($mime_type, '.');
// Is this extension supported?
if (isset($this->mime_types[$extension]))
{
$mime_type =& $this->mime_types[$extension];
if (is_array($mime_type))
{
$mime_type = current($mime_type);
}
}
}
$header = 'Content-Type: '.$mime_type;
$this->headers[] = array($header, TRUE);
return $this;
}
// --------------------------------------------------------------------
/**
* Set HTTP Status Header
* moved to Common procedural functions in 1.7.2
*
* @access public
* @param int the status code
* @param string
* @return void
*/
function set_status_header($code = 200, $text = '')
{
set_status_header($code, $text);
return $this;
}
這邊看得到為了維持與舊版的相容性所留下的痕跡。
// --------------------------------------------------------------------
/**
* Enable/disable Profiler
*
* @access public
* @param bool
* @return void
*/
function enable_profiler($val = TRUE)
{
$this->enable_profiler = (is_bool($val)) ? $val : TRUE;
return $this;
}
一個漂亮的防禦性編程。不是布林值的一律視為TRUE。只用了一行。
不期待回傳值的函數看來全都寫成了回傳 $this。
// --------------------------------------------------------------------
/**
* Set Profiler Sections
*
* Allows override of default / config settings for Profiler section display
*
* @access public
* @param array
* @return void
*/
function set_profiler_sections($sections)
{
foreach ($sections as $section => $enable)
{
$this->_profiler_sections[$section] = ($enable !== FALSE) ? TRUE : FALSE;
}
return $this;
}
// --------------------------------------------------------------------
/**
* Set Cache
*
* @access public
* @param integer
* @return void
*/
function cache($time)
{
$this->cache_expiration = ( ! is_numeric($time)) ? 0 : $time;
return $this;
}
// --------------------------------------------------------------------
/**
* Display Output
*
* All "view" data is automatically put into this variable by the controller class:
*
* $this->final_output
*
* This function sends the finalized output data to the browser along
* with any server headers and profile data. It also stops the
* benchmark timer so the page rendering speed and memory usage can be shown.
*
* @access public
* @param string
* @return mixed
*/
function _display($output = '')
{
// Note: We use globals because we can't use $CI =& get_instance()
// since this function is sometimes called by the caching mechanism,
// which happens before the CI super object is available.
global $BM, $CFG;
// Grab the super object if we can.
if (class_exists('CI_Controller'))
{
$CI =& get_instance();
}
// --------------------------------------------------------------------
// Set the output data
if ($output == '')
{
$output =& $this->final_output;
}
// --------------------------------------------------------------------
// Do we need to write a cache file? Only if the controller does not have its
// own _output() method and we are not dealing with a cache file, which we
// can determine by the existence of the $CI object above
if ($this->cache_expiration > 0 && isset($CI) && ! method_exists($CI, '_output'))
{
$this->_write_cache($output);
}
若是要求CI在controller內cache頁面，會使用
$this->output->cache(1); //tells the CI to cache this page for 1 minute
設定快取時間。所以若是cache_expiration大於零，表示有被要求快取此頁面。
controller若是有定義_output函數，則Output類別不會將結果直接echo到瀏覽器，而是丟給_output去處理。
那樣的話，此處不做cache，因為不知道controller拿到資料會接著做什麼修改。
此_display函數有時是被快取機制所呼叫。那樣的話，便不需要寫入cache。
至於如何得知是被快取機制呼叫？是利用isset($CI)判定全域變數的存在。
我認為這很醜、光看isset($CI)也看不出是在判斷什麼東西。code可讀性很差。
我認為這是濫用全域變數的一個例子。
// --------------------------------------------------------------------
// Parse out the elapsed time and memory usage,
// then swap the pseudo-variables with the data
$elapsed = $BM->elapsed_time('total_execution_time_start', 'total_execution_time_end');
if ($this->parse_exec_vars === TRUE)
{
$memory = ( ! function_exists('memory_get_usage')) ? '0' : round(memory_get_usage()/1024/1024, 2).'MB';
$output = str_replace('{elapsed_time}', $elapsed, $output);
$output = str_replace('{memory_usage}', $memory, $output);
}
// --------------------------------------------------------------------
// Is compression requested?
if ($CFG->item('compress_output') === TRUE && $this->_zlib_oc == FALSE)
{
if (extension_loaded('zlib'))
{
if (isset($_SERVER['HTTP_ACCEPT_ENCODING']) AND strpos($_SERVER['HTTP_ACCEPT_ENCODING'], 'gzip') !== FALSE)
{
ob_start('ob_gzhandler');
}
}
}
// --------------------------------------------------------------------
// Are there any server headers to send?
if (count($this->headers) > 0)
{
foreach ($this->headers as $header)
{
@header($header[0], $header[1]);
}
}
// --------------------------------------------------------------------
// Does the $CI object exist?
// If not we know we are dealing with a cache file so we'll
// simply echo out the data and exit.
if ( ! isset($CI))
{
echo $output;
log_message('debug', "Final output sent to browser");
log_message('debug', "Total execution time: ".$elapsed);
return TRUE;
}
// --------------------------------------------------------------------
// Do we need to generate profile data?
// If so, load the Profile class and run it.
if ($this->enable_profiler == TRUE)
{
$CI->load->library('profiler');
if ( ! empty($this->_profiler_sections))
{
$CI->profiler->set_sections($this->_profiler_sections);
}
// If the output data contains closing and