I'm using Netbeans IDE, it shows a warning next to undeclared variables - very useful.
If I have this at the top of a file
global $CFG;
then the warnings go away because the variable has been declared.
But is this good practice? Are they any advantages? The code still works without the declaration.
Note: This is for files that have code outside of functions.
it is good practice to declare variables before using them. Declaring them as global within the global scope is superfluous though. You could just do
Instead of doing
global $CFG;
you can just do
$CFG;
The only time declaring them with the global prefix is "useful" is when you do it inside a function to access a globally scoped variable from within the function - but this is usually bad practice, very few cases where this is absolutely necessary.
No, if you wish to use a variable outside of its scope (for example inside a function) you may pass it or globalize it inside the function
function xoxo(){
global $var;
}
有两件事让我对以这种方式“声明”变量保持警惕。
首先，任何函数之外的大量代码可能意味着您的代码需要重构。在您的代码的顶层，您可能有几行调用脚本或页面的主要操作，但是说您的声明将放在“文件的顶部”表明还有更多。
其次，在 PHP 中“声明”一个变量通常与赋予它某种初始值同义。例如，$params = array()在构建模板参数列表之前进行设置，例如$params['foo'] = get_foo(). 这种初始化应始终与使用它的代码保持接近，这样如果您稍后重新分解它，代码就会随之而来。
为什么总是初始化一个变量是一个好主意的一个例子是，如果你最终将整个代码块放在某种循环中。在上面的例子中，如果我渲染了多个模板并且忘记了初始化$params，$params['foo']最终可能会被传递给每个模板。