PHP学习之预定义变量(实例讲解)

超全局变量

超全局变量–超全局变量是全部作用域中始终可用的内置变量

$GLOBALS

一个包含了全部变量的全局组合数组。变量的名字就是数组的键。

<?php
function test() {
  $foo = "local variable";
  echo '$foo in global scope: ' . $GLOBALS["foo"] . "\n";
  echo '$foo in current scope: ' . $foo . "\n";
}
$foo = "Example content";
test();
?>
以上例程的输出类似于：
$foo in global scope: Example content
$foo in current scope: local variable

$_SERVER

<?PHP
echo "<pre>";
var_dump($_SERVER);
output:
array (size=35)
 'HTTP_HOST' => string 'localhost' (length=9)
 'HTTP_CONNECTION' => string 'keep-alive' (length=10)
 'HTTP_UPGRADE_INSECURE_REQUESTS' => string '1' (length=1)
 'HTTP_USER_AGENT' => string 'Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.104 Safari/537.36 Core/1.53.3538.400 QQBrowser/9.6.12501.400' (length=153)
 'HTTP_ACCEPT' => string 'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8' (length=74)
 'HTTP_REFERER' => string 'http://localhost/test/' (length=22)
 'HTTP_ACCEPT_ENCODING' => string 'gzip, deflate, sdch' (length=19)
 'HTTP_ACCEPT_LANGUAGE' => string 'zh-CN,zh;q=0.8' (length=14)
 'PATH' => string '%APPCAN_PATH%;D:\Work\python2.7\;D:\Work\python2.7\Scripts;C:\ProgramData\Oracle\Java\javapath;C:\WINDOWS\system32;C:\WINDOWS;C:\WINDOWS\System32\Wbem;C:\WINDOWS\System32\WindowsPowerShell\v1.0\;D:\wampserver\mysql\bin;D:\Work\JAVA\tomcat\bin;D:\Work\Mozilla Firefox\firefox.exe;D:\Work\phantomjs\bin;D:\Work\chormedriver;C:\WINDOWS\system32\config\systemprofile\.dnx\bin;C:\Program Files\Microsoft DNX\Dnvm\;C:\Program Files\Microsoft SQL Server\130\Tools\Binn\;D:\wampserver\php;C:\ProgramData\ComposerSetup\bi'... (length=607)
 'SystemRoot' => string 'C:\WINDOWS' (length=10)
 'COMSPEC' => string 'C:\WINDOWS\system32\cmd.exe' (length=27)
 'PATHEXT' => string '.COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH;.MSC' (length=53)
 'WINDIR' => string 'C:\WINDOWS' (length=10)
 'SERVER_SIGNATURE' => string '' (length=0)
 'SERVER_SOFTWARE' => string 'Apache/2.4.18 (Win64) OpenSSL/1.0.2g PHP/5.6.19' (length=47)
 'SERVER_NAME' => string 'localhost' (length=9)
 'SERVER_ADDR' => string '::1' (length=3)
 'SERVER_PORT' => string '80' (length=2)
 'REMOTE_ADDR' => string '::1' (length=3)
 'DOCUMENT_ROOT' => string 'D:/wampserver/www' (length=17)
 'REQUEST_SCHEME' => string 'http' (length=4)
 'CONTEXT_PREFIX' => string '' (length=0)
 'CONTEXT_DOCUMENT_ROOT' => string 'D:/wampserver/www' (length=17)
 'SERVER_ADMIN' => string 'admin@example.com' (length=17)
 'SCRIPT_FILENAME' => string 'D:/wampserver/www/test/$_SERVER.php' (length=35)
 'REMOTE_PORT' => string '57305' (length=5)
 'GATEWAY_INTERFACE' => string 'CGI/1.1' (length=7)
 'SERVER_PROTOCOL' => string 'HTTP/1.1' (length=8)
 'REQUEST_METHOD' => string 'GET' (length=3)
 'QUERY_STRING' => string '' (length=0)
 'REQUEST_URI' => string '/test/$_SERVER.php' (length=18)
 'SCRIPT_NAME' => string '/test/$_SERVER.php' (length=18)
 'PHP_SELF' => string '/test/$_SERVER.php' (length=18)
 'REQUEST_TIME_FLOAT' => float 1510122616.201
 'REQUEST_TIME' => int 1510122616

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