Why are there half a square brackets behind the many function parameters in the PHP manual? What's the point of these parentheses?

Source: Internet
Author: User
Why are there half a square brackets behind the many function parameters in the PHP manual? What's the point of these parentheses?
Always have this question, Google, Baidu has no answer, do not know if anyone can give a solution.
Thank

Reply content:

Why are there half a square brackets behind the many function parameters in the PHP manual? What's the point of these parentheses?
Always have this question, Google, Baidu has no answer, do not know if anyone can give a solution.
Thank

array array_filter ( array $array [, callable $callback [, int $flag = 0 ]] )

You refer to the $callback $flag brackets in the two arguments, indicating that these are optional parameters

  • Contact Us

    The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion; products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the content of the page makes you feel confusing, please write us an email, we will handle the problem within 5 days after receiving your email.

    If you find any instances of plagiarism from the community, please send an email to: info-contact@alibabacloud.com and provide relevant evidence. A staff member will contact you within 5 working days.

    A Free Trial That Lets You Build Big!

    Start building with 50+ products and up to 12 months usage for Elastic Compute Service

    • Sales Support

      1 on 1 presale consultation

    • After-Sales Support

      24/7 Technical Support 6 Free Tickets per Quarter Faster Response

    • Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.