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The difference between null and empty in php: empty is a function that checks whether a variable is empty, true; is returned if the variable is empty, and null is a data type, indicating that a variable has no value that is empty, and is represented as null when the variable is assigned to mull, not assigned, or by unset ().

This article operating environment: Windows10 system, PHP7.1 version, Dell G3 computer.

What is the difference between null and empty in php

Null means that a variable has no value. There are three cases in which a variable is null:

1. Is assigned to NULL.

two。 Has not been assigned yet.

3. By unset ().

The 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 when its value is equal to FALSE, then it is considered nonexistent. Empty () does not generate a warning if the variable does not exist.

Expressions, not just variables, are supported after empty () 5.5.

Grammar

Bool empty (mixed $var)

Parameter description:

Var: the 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 take effect:

Empty (trim ($name))

Instead, you should use:

Trim ($name) = = false

Empty () does 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 if var exists and is a non-empty non-zero value. Otherwise, TRUE is returned.

The following variables are considered empty:

"" (empty string)

0 (0 as an integer)

0.0 (as 0 of a floating point number)

"0" (as 0 of the string)

NULL

FALSE

Array () (an empty array)

$var; (a variable that is declared but has no value)

Example

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