What is the difference between null and empty string in php

In php, null and empty string have different types. The data type of empty string is "string", while the data type of null is "NULL"; and the empty string will occupy a memory, but There is nothing in this memory, but null means that this thing does not exist at all, and the memory will not be opened.

The operating environment of this tutorial: windows7 system, PHP7.1 version, DELL G3 computer

Empty string'' and NULL The difference

Empty strings and NULL in PHP are both stored with a value of 0, but their types are different. The former is string, while the latter is NULL, visible string ('') , NULL values ​​are equal but have different types.

The empty string will occupy a memory, but there is nothing in the memory, but null means that there is no such thing at all, and it will not open up the memory.

$str1 = "";
$str2 = null;
var_dump($str1); // 空字符串
var_dump($str2); // NULL
if($str1){echo "a";}else{echo "b";}; // b
if($str2){echo "c";}else{echo "d";}; // d
echo gettype($str1); // string
echo gettype($str2); // null

Specific instructions:

1. For example, a disabled person, although disabled, can call other methods, such as eating. And without such a person, it would be impossible to eat.

2. For example, if you have a wallet but no money, it is different from not having a wallet.

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