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现在自学PHP 看的是兄弟连的视频教程 学到变量范围的时候 视频老师的例子是  :
$a = 10;
function demo(){
       $a+=10;
}
demo();

可是我在照做例子的时候出现
Notice: Undefined variable: a  这样的错误提示,在函数里先给$a赋值就没问题了。我的是5.3+的。是不是php版本的问题?


回复讨论(解决方案)

这个程序中在函数中 $a是一个局部变量,如果你想引用函数外你预先声明的变量$a你必须要加入global 
        $a=10;
        function demo()
        {
                global $a;
                $a+=5;
                echo $a;
        }
        demo();
        echo $a;
?>

所有的版本都是这样

这个程序中在函数中 $a是一个局部变量,如果你想引用函数外你预先声明的变量$a你必须要加入global 
        $a=10;
        function demo()
        {
                global $a;
                $a+=5;
                echo $a;
        }
        demo();
        echo $a;
?>
不错!~

我知道全局变量要加GLOBAL。可是视频教程的例子没有加GLOBAL 一样可以执行,没错误提示。我在本地照做就提示 Notice: Undefined variable: a这个错误,不知道是怎么回事

我知道全局变量要加GLOBAL。可是视频教程的例子没有加GLOBAL 一样可以执行,没错误提示。我在本地照做就提示 Notice: Undefined variable: a这个错误,不知道是怎么回事
通过自己尝试老师的代码,让你意识到,变量,全局变量,局部变量的作用域的重要性,远比弄清楚老师用的哪个版本实现的这个代码,跟重要

因为他把notice错误级别屏蔽了。
你在首行加上:error_reporting(E_ALL & ~E_NOTICE); 也不会报错。

我明白你的意思,但是这个问题还是困惑着我,只想弄清楚是不是PHP版本的问题,才导致这个错误,下次会注意这个问题。到现在也没有人直接回答我这个问题!!!

与PHP版本无关,原因我在#6说明了。

明白了,谢谢版主的回答,试了一下还真是这样。

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