PHP empty() function

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 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() supports expressions after version 5.5, not just variables.

Version requirements: PHP 4, PHP 5, PHP 7

grammar

 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 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 .

return value

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

The following variables are considered empty:

"" (empty string)

0 (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

Example

The execution result is as follows:

 $ivar1 is empty or 0. $istr1 string is not empty or 0.