lamp架構中.user.ini文件在修改php配置參數中的應用分析
Since PHP 5.3.0, PHP includes support for configuration INI files on a per-directory basis. These files are processed only by the CGI/FastCGI SAPI（wyq：user.ini只有在SAPI是CGI/FastCGI的時候有效，即如果SAPI的接口選mod_php模塊時候無效）. This functionality obsoletes the PECL htscanner extension. If you are running PHP as Apache module, use .htaccess files for the same effect.
In addition to the main php.ini file, PHP scans for INI files in each directory, starting with the directory of the requested PHP file, and working its way up to the current document root (as set in $_SERVER[‘DOCUMENT_ROOT’]). In case the PHP file is outside the document root, only its directory is scanned.
Only INI settings with the modes PHP_INI_PERDIR and PHP_INI_USER will be recognized in .user.ini-style INI files.
Two new INI directives, user_ini.filename and user_ini.cache_ttl control the use of user INI files.
user_ini.filename sets the name of the file PHP looks for in each directory; if set to an empty string, PHP doesn’t scan at all. The default is .user.ini.
user_ini.cache_ttl controls how often user INI files are re-read. The default is 300 seconds (5 minutes).