我遇到了莫名其妙的问题，我的网站无法正常访问，这个问题是怎么发生的？我的网站之前运行流畅，出现这个问题后我重启了我的主机，我的网站可以正常访问了。
httpd error_log 文件内容如下：
[Sun Aug 20 09:20:03 2017] [notice] Apache/2.2.15 (Unix) DAV/2 PHP/5.3.3 mod_ssl/2.2.15 OpenSSL/1.0.1e-fips configured -- resuming normal operations
PHP Fatal error: Call to undefined function is_resource() in /var/www/html/i2active/application/third_party/log4php/appenders/LoggerAppenderFile.php on line 164
PHP Fatal error: Call to undefined function is_resource() in /var/www/html/i2active/application/third_party/log4php/appenders/LoggerAppenderFile.php on line 164
PHP Warning: (Registered shutdown functions) Unable to call _shutdown_handler() - function does not exist in Unknown on line 0
PHP Warning: (Registered shutdown functions) Unable to call _shutdown_handler() - function does not exist in Unknown on line 0
PHP Warning: (Registered shutdown functions) Unable to call session_write_close() - function does not exist in Unknown on line 0
PHP Warning: (Registered shutdown functions) Unable to call session_write_close() - function does not exist in Unknown on line 0