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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