问题
I've been handed a pile of code that includes a lot of require/include statments (mixed between require and require_once). Sometimes, the path has parenthesis around it, i.e. require_once (JPATH_COMPONENT.DS.'controller.php');, and other times there isn't: require_once $path;.
The php docs for include mention this, but aren't specific. Should I remove the parenthesis when I find them, or is it ok to leave them alone? When writing further require/include statements, are there specific cases where I should use them?
回答1:
You are allowed to use parentheses in 'include/require' not because include allows it itself but because you can use parentheses around any string or number in PHP for grouping.
So for example, "dog" is equivalent to ("dog"), ("dog")."dog" is equivalent to "dog"."dog", etc.
Parentheses become useful when you use complex expressions involving calculations and string concatenations but in such a simple case, they are simply allowed and perform an unnecessary and harmless "grouping" of a single string value.
回答2:
There is no issue with leaving them or taking them out, at the end of the day it is up to the comfort of the developer.
Personally, I leave them off. I think it looks a little cleaner, and the IDE syntax coloring works a bit better.
回答3:
Both syntaxes are valid. So, it's up to you. :)
The documentation explains:
Because include is a special language construct, parentheses are not needed around its argument.
来源：https://stackoverflow.com/questions/10918598/when-should-i-use-parenthesis-in-require-include-statements