在PHP函数中访问全局变量
问题描述:
根据大多数编程语言的作用域规则,我可以访问在函数内部定义的变量,但是为什么此代码不起作用?
According to the most programming languages scope rules, I can access variables that are defined outside of functions inside them, but why doesn't this code work?
<?php
$data = 'My data';
function menugen() {
echo "[" . $data . "]";
}
menugen();
?>
输出为[]
.
答
它不起作用,因为您必须声明要访问的全局变量:
It is not working because you have to declare which global variables you'll be accessing:
$data = 'My data';
function menugen() {
global $data; // <-- Add this line
echo "[" . $data . "]";
}
menugen();
否则,您可以作为$GLOBALS['data']
来访问它.参见 变量范围 .
Otherwise you can access it as $GLOBALS['data']
. See Variable scope.
即使有些偏离主题,我还是建议您完全避免使用全局变量,而更希望将其作为参数传递.
Even if a little off-topic, I'd suggest you avoid using globals at all and prefer passing as parameters.