本文主要为大家分享一篇php学习之预定义变量(实例讲解)，具有很好的参考价值，希望对大家有所帮助。一起跟随小编过来看看吧，希望能帮助到大家。
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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以上就是php预定义变量详解的详细内容。