php中global和$GLOBALS最浅显易懂的解释

　　官方文档：

global指对变量的引用或者叫指针，$GLOBALS则是变量本身；

$var1 = 1;
        $var2 = 2;
        function fun(){
          $GLOBALS['var2'] = &$GLOBALS['var1'];
          echo $GLOBALS['var2'];
          $GLOBALS['var2'] = 3;
        }

        fun();
        echo $var2;
        echo $var1;
        echo "\r\n";

        function fun1(){
          global $var1, $var2;
          $var2 = &$var1;
          echo $var2;
          echo "\r\n";
          $var2 = 3;
        }

        fun1();
        echo $var2;
        echo $var1;

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