$GLOBALS['var'] 是外部的全局变量$var本身，修改或者unset，$GLOBALS['var'] 都会影响外部的全局变量$var ~~~ $var1 = 1; $var2 = 2; function test() { $GLOBALS['var2'] = $GLOBALS['var1']; } test(); echo $var2;//输出1 ~~~ ~~~ $var1 = 1; $var2 = 2; function test() { unset($GLOBALS['var2']) ; } test(); echo $var2;// 输出错误 Undefined variable: var2 ~~~ * * * * * global $var 是外部$var的别名引用，修改$var会影响外部的全局变量$var，但是使用unset 并不会 ~~~ $var1 = 1; $var2 = 2; function test() { global $var1, $var2; $var2 = $var1; } test(); echo $var2; // 输出 1 ~~~ ~~~ $var2 = 2; function test() { global $var2; unset($var2) ; } test(); echo $var2; // 输出 2 ~~~ 资料来源： https://www.cnblogs.com/Life-Record/p/4964344.html