PHP——超全局变量_学习笔记

什么是超全局变量

PHP 中的许多预定义变量都是“超全局的”，这意味着它们在一个脚本的全部作用域中都可用。在函数或方法中无需执行 global $variable; 就可以访问它们。

    $_SERVER   //查看服务器信息    $_GET      //地址栏参数    $_POST     //表单提交的值    $_REQUEST//接受$_GET或$_POST的值    $_FILES        //文件上传    $_COOKIE   //跟踪用户状态    $_SESSION  //跟踪用户状态    $GLOBALS   //获取所有全局变量的值

$_SERVER:
可以查看服务器的信息，里面保存关于报头、路径和脚本位置的信息。
下面打印出来看下：

<?phpprint_r($_SERVER);?>

结果如下：

Array(    [HTTP_HOST] => localhost    [HTTP_CONNECTION] => keep-alive    [HTTP_CACHE_CONTROL] => max-age=0    [HTTP_ACCEPT] => text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8    [HTTP_UPGRADE_INSECURE_REQUESTS] => 1    [HTTP_USER_AGENT] => Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/48.0.2564.116 UBrowser/5.6.11466.7 Safari/537.36    [HTTP_REFERER] => http://localhost/PHP/php7/    [HTTP_ACCEPT_ENCODING] => gzip, deflate    [HTTP_ACCEPT_LANGUAGE] => zh-CN,zh;q=0.8    [PATH] => C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;C:\Windows\System32\WindowsPowerShell\v1.0\;    [SystemRoot] => C:\Windows    [COMSPEC] => C:\Windows\system32\cmd.exe    [PATHEXT] => .COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH;.MSC    [WINDIR] => C:\Windows    [SERVER_SIGNATURE] => <address>Apache/2.4.9 (Win64) PHP/5.5.12 Server at localhost Port 80</address>    [SERVER_SOFTWARE] => Apache/2.4.9 (Win64) PHP/5.5.12    [SERVER_NAME] => localhost    [SERVER_ADDR] => ::1    [SERVER_PORT] => 80    [REMOTE_ADDR] => ::1    [DOCUMENT_ROOT] => D:/www/    [REQUEST_SCHEME] => http    [CONTEXT_PREFIX] =>     [CONTEXT_DOCUMENT_ROOT] => D:/www/    [SERVER_ADMIN] => [e-mail]    [SCRIPT_FILENAME] => D:/www/PHP/php7/demo.php    [REMOTE_PORT] => 52683    [GATEWAY_INTERFACE] => CGI/1.1    [SERVER_PROTOCOL] => HTTP/1.1    [REQUEST_METHOD] => GET    [QUERY_STRING] =>     [REQUEST_URI] => /PHP/php7/demo.php    [SCRIPT_NAME] => /PHP/php7/demo.php    [PHP_SELF] => /PHP/php7/demo.php    [REQUEST_TIME_FLOAT] => 1460548562.994    [REQUEST_TIME] => 1460548562)