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认证高级PHP讲师
If parentheses are not added, the returned result is the groups matched by regular expressions;
If parentheses are added, all groups will be returned, including unmatched groups.
The official document is very clear, I just translated it for you.
Explanation in python3-cookbook
![[Web front-end] Node.js quick start](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
If parentheses are not added, the returned result is the groups matched by regular expressions;
If parentheses are added, all groups will be returned, including unmatched groups.
The official document is very clear, I just translated it for you.
Explanation in python3-cookbook