What is the NULL data type in PHP? How to use it? (Source code attached)

Want to know what is the NULL data type in PHP? Regarding PHP data types, I think this article will help you understand a lot and learn a lot, so let’s take a look! ! !

#1: What is NULL?

For the word MULL, it represents empty, not error (false) and 0, nor our commonly used spaces;

2: For NULL Type, there are three situations where an empty type will appear:

• No value is assigned to the variable;

• By assigning a value to a variable, it is stated in advance that the value of the variable is NULL

• Use the unset() function to destroy the variable

3: Regarding the NULL type, there are two closely related functions, one is the empty() function and the other isset() function; the following is a separate code demonstration.

For the isset() function: One or more variables can be passed in the brackets, but what we need to pay attention to is that the variables must be separated by commas. During this period, if there is a If the variable is null, the return value is false, otherwise it is true;

If the input is empty (null), the code demonstration is as follows:

<?php
$shangke=null;
//isset只要传入的值不为空（null）,其返回值都是真（true）
$result = isset($shangke);
var_dump($result);
?>

The execution result is as follows:

If the input is (0), the code demonstration is as follows:

<?php
$shangke=0;
//isset只要传入的值不为空（null）,其返回值都是真（true）
$result = isset($shangke);
var_dump($result);
?>

The execution result is as follows:

About the empty() function: It can pass a variable into the brackets. If the value of this variable is false or null, the return value is true (true);

The code demonstration is as follows:

<?php
$shangke=null;
if(empty($shangke)){
    echo &#39;去上课&#39;;
}else{
    echo &#39;不去上课&#39;;
}
?>

The result of the code is as follows:

As shown by running the code: the execution result is true.

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