php设置环境变量
实例：

$g_config['root'] =dirname(realpath(__FILE__)); set_include_path($g_config['root'].'/pear'. PATH_SEPARATOR . $g_config['root'] . '/cas' . PATH_SEPARATOR .get_include_path());

批注：
1，realpath(__FILE__)
2，get_include_path()
3，set_include_path()