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.