“父”文件中定义的PHP变量无法在“必需”文件中识别

I am trying to access a variable defined in parent file from inside the required file, like this:

<<< parent.php >>>

$controller = 'index';
require ('child.php');

<<< child.php >>>

echo $controller;

somehow, I am receiving a null output, which means that the variable is not accessible via child.php.. am I doing something wrong here? if possible, please let me know how I can call the above variable in my child.php file, if above seems to be wrong.

Regards
Nikhil Gupta

Is your variable declared outside a function body? If not, it needs to be.

Also, when calling the variable from your child file, try "initializing" it with the Global keyword before using it...

like

Global $myParentVariable;

...then try printing it. Also, for debugging purposes, set the variable to a constant in your parent file instead of deriving the value in some function. In other words, make sure it's not a function turning the value to null. (I see you are doing that in the post - but not sure if you modified it for simplicity)

That is strange. Try to see if variable is part of defined variables:

$vars = get_defined_vars();
print_r($vars);

Also, If your variable exists in a function, you can globalize it with global keyword.

Alright, Got the issue here. It was a mistake of mine, I guess. The error was not in the above lines, but somehow another variable was rather than accessing the parent php, was accessing the child php directly.

So, guess, it works out now, why the variables were not available.