apache_event_php-fpm 示意图：
nginx-php-fpm示意图：
Worker-Master-Server
TCP-Nginx_PHP
Nginx-FastCGI
1、使用$_GET 获取所有参数，php7 会多出一个参数：_url ，例如访问的地址
http://127.0.0.1/Home/String/index2?a=12&b=19
此时的的参数_url = "Home/String/index2"
2、在PHP7 中为一个Error：PHP Notice: Undefined index: HTTP_USER_AGENT in line 2
php5.9则为一个notice
2017/03/27 10:58:09 [error] 5286#0: *851 FastCGI sent in stderr: "PHP message: PHP Notice: Undefined index: HTTP_USER_AGENT in /home/UserAgent.php on line 9" while reading response header from upstream
解决：http://stackoverflow.com/questions/16330496/php-notice-undefined-index-http-user-agent-in-line-2
if(!empty($_SERVER['HTTP_USER_AGENT'])){ $user_agent = $_SERVER['HTTP_USER_AGENT']; } else { $user_agent = ''; }
3、NULL 合并运算符 ，PHP7才正式加入了??这个运算符：
// 获取user参数的值(如果为空，则用'nobody') $username = $_GET['user'] ?? 'nobody'; // 等价于: $username = isset($_GET['user']) ? $_GET['user'] : 'nobody';
4、php-fpm 没有启动的后果
2017/03/31 20:56:19 [crit] 19288#0: *1 connect() to unix:/var/run/php7.0.9-fpm.sock failed (2: No such file or directory) while connecting to upstream, client: 127.0.0.1,
server: www.phalcon3.com, request: "GET /index.php HTTP/1.1", upstream: "fastcgi://unix:/var/run/php7.0.9-fpm.sock:", host: "127.0.0.1"
tinywan@tinywan:/usr/local/nginx/logs$ ll /var/run/php7.0.9-fpm.sock
ls: 无法访问'/var/run/php7.0.9-fpm.sock': 没有那个文件或目录
搞了半天，原来php-fmp 没有启动，
