PHP empty() Function

PHP Available Functions

empty()The function is used to check whether a variable is empty.

empty() determines whether a variable is considered empty. A variable is considered empty when it does not exist, or when its value equals FALSE. If the variable does not exist, empty() does not generate a warning.

Since PHP 5.5, empty() supports expressions, not just variables.

Version requirements: PHP 4, PHP 5, PHP 7

Syntax

bool empty ( mixed $var )

Parameter description:

• $var: The variable to be checked.

Note: Before PHP 5.5, empty() only supported variables; anything else would cause a parse error. In other words, the following code will not work:

empty(trim($name))

Instead, use:

trim($name) == false

empty() does not generate a warning, even if the variable does not exist. This meansempty()it is essentially!isset($var) || $var == falseequivalent.

Return Value

Returns FALSE when var exists and is a non-empty, non-zero value; otherwise returns TRUE.

The following variables are considered empty:

• ""(empty string)
• 0(0 as an integer)
• 0.0(0 as a float)
• "0"(0 as a string)
• NULL
• FALSE
• array()(an empty array)
• $var;(a variable declared, but with no value)

Example

The output is as follows:

$ivar1 为空或为 0。
$istr1 字符串不为空或不为0。

PHP Available Functions