What is the difference between null and empty in php
The difference between null and empty in php: empty is a function used to check whether a variable is empty. If the variable is empty, it returns true; and null is a data type, indicating that a variable has no value and is empty. , when the variable is assigned a value of mull, is not assigned a value, or is unset(), it is expressed as null.

The operating environment of this article: Windows 10 system, PHP version 7.1, Dell G3 computer.
What is the difference between null and empty in php
null means that a variable has no value. There are three situations when a variable is null:
1. It is assigned a value of NULL.
2. Has not been assigned a value.
3. By unset().
empty() function is used to check whether a variable is empty.
empty() Determines whether a variable is considered empty. When a variable does not exist, or its value is equal to FALSE, then it is considered not to exist. empty() does not generate a warning if the variable does not exist.
empty() After version 5.5, it supports expressions, not just variables.
Syntax
bool empty ( mixed $var )
Parameter description:
$var: Variable to be checked.
Note: Prior to PHP 5.5, empty() only supported variables; anything else would cause a parsing error. In other words, the following code will not work:
empty(trim($name))
Instead, you should use:
trim($name) == false
empty() and will not generate a warning, even if the variable does not exist. This means that empty() is essentially equivalent to !isset($var) || $var == false.
Returns FALSE when var exists and is a non-empty and non-zero value, otherwise returns TRUE.
The following variables will be considered empty:
"" (empty string)
0 (as 0 as an integer)
0.0 (0 as a floating point number)
"0" (0 as a string)
NULL
- ##FALSE ##array() (an empty array)
- $var; (a variable declared but without a value)
- Example
<?php
$ivar1=0;
$istr1='Runoob';
if (empty($ivar1))
{
echo '$ivar1' . " 为空或为 0。" . PHP_EOL;
}
else
{
echo '$ivar1' . " 不为空或不为 0。" . PHP_EOL;
}
if (empty($istr1))
{
echo '$istr1' . " 为空或为 0。" . PHP_EOL;
}
else
{
echo '$istr1' . " 字符串不为空或不为0。" . PHP_EOL;
}
?>Recommended study: "
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