__FILE__、__DIR__区别
__FILE__=D:\Soft\xampp\htdocs\test\test.php __DIR__=D:\Soft\xampp\htdocs\test getcwd()=D:\Soft\xampp\htdocs\test $_SERVER["SCRIPT_FILENAME"]=D:/Soft/xampp/htdocs/test/test.php

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__FILE__=D:\Soft\xampp\htdocs\test\test.php __DIR__=D:\Soft\xampp\htdocs\test getcwd()=D:\Soft\xampp\htdocs\test $_SERVER["SCRIPT_FILENAME"]=D:/Soft/xampp/htdocs/test/test.php