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;
$istr1=&#39;Runoob&#39;;
if (empty($ivar1))
{
    echo &#39;$ivar1&#39; . " 为空或为 0。" . PHP_EOL;
}
else
{
    echo &#39;$ivar1&#39; . " 不为空或不为 0。" . PHP_EOL;
}
if (empty($istr1))
{
    echo &#39;$istr1&#39; . " 为空或为 0。" . PHP_EOL;
}
else
{
    echo &#39;$istr1&#39; . " 字符串不为空或不为0。" . PHP_EOL;
}
?>

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