Use $GLOBALS['three'] = 'china'; inside the function to declare global variables, and use it outside the function to prompt Undefined variable '$three'
is not an error, it is a warning, you can type
normally
亮色时光1546 days ago929

Question

It's not an error, it's a warning. It can be typed normally.

Use $GLOBALS['three'] = 'china'; inside the function to declare global variables, and use it outside the function to prompt Undefined variable '$three'