PHP: empty, isset, is_null, array (0), array (), array (""), 0, "0", "", "null", NULL summary

Source: Internet
Author: User
PHP: empty, isset, is_null, array (0), array (), array (), 0, 0, null, NULL summary through the following program to detect

$a=0;if(empty($a)){echo "yes|";}else{echo "no|";}if(isset($a)){echo "yes|";}else{echo "no|";}if(is_null($a)){echo "yes|";}else{echo "no|";}if($a){echo "yes|";}else {echo "no|";}

The result of getting different values for $ a is as follows:



Summary:

Empty

1. the variable value is null $ var = "";

2. the variable value is string 0, number 0 $ var = 0, or $ var = "0 ″

3. the variable value is flase $ var = flase;

4. all NULL values are NULL.

5 empty array $ arr = array ();

6. only variables with no value assigned $ var are defined;

Isset

Check whether a variable has been set and is not NULL (Determine if a variable is set and is not NULL)

Is_null

Judge null

Judge whether it is false

1. the variable value is null $ var = "";

2. the variable value is string 0, number 0 $ var = 0, or $ var = "0 ″

3. the variable value is flase $ var = flase;

4. all NULL values are NULL.

5 empty array $ arr = array ();

6. only variables with no value assigned $ var are defined;

Full false

Copyright Disclaimer: This article is an original article by the blogger and cannot be reproduced without the permission of the blogger.

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.