In PHP, the difference between 0 and null

In PHP, the difference between 0 and null

I don’t know that when you store fields with default data of 0 in the MySQL database, but there is an error when judging 0 or Null in the program, because 0 and Null is not completely equal. It seems like a simple problem, but it is very tricky to judge. The values ​​of Null and 0 are the same, but the types are not the same. To put it simply, it is the difference between == and ===. The first == only needs the same value, but === not only requires the same value but also the same type of value.

Null is a special type, two types are Null, such as the following code:

1. $var = NULL;

2. $var;

3.0, "0", NULL, and objects without any attributes will be considered empty.

Look at the example below

<?
 
$str1 = null;
 
$str2 = 0;
 
echo $str1==$str2 ? ‘相等’ : ‘不相等’;
 
$str3 = "";
 
$str4 = 0;
 
echo $str3==$str4 ? ‘相等’ : ‘不相等’;
 
$str5 = 0;
 
$str6 = &#39;0&#39;;
 
echo $str5===$str6 ? ‘相等’ : ‘不相等’;
 
$str7=0;
 
$str= null ;
 
echo $str7==$str8 ? ‘相等’ : ‘不相等’;
 
?>

Run result

'Equal''Equal''Not equal''Equal'

So, 0 and Null The values ​​are equal, but their types are not. Okay, let’s briefly summarize the difference between PHP 0 and null. In short, if you are not clear about the difference, just make a few more judgments.