PHP Manual: Determine whether a variable is empty

Description

bool empty ( mixed $var )

Determine whether a variable is considered to be empty. A variable is considered empty if it does not exist or if its value equals FALSE. empty does not generate a warning if the variable does not exist.

Parameters

var

Variable to be checked

Note:
Prior to PHP 5.5, empty only supports variables; anything else will result in a parse error. In other words, the following will not work: empty(trim($name)). Instead, use trim($name) == false.

No warning is generated if the variable does not exist. That means empty is essentially the concise equivalent to !isset($var) || $var == false.

Return Values

Returns FALSE if var exists and has a non-empty, non-zero value. Otherwise returns TRUE.

The following things are considered to be empty:

"" (an 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 without a value)

Changelog

Version	Description
5.5.0	empty now supports expressions, rather than only variables.
5.4.0	Checking non-numeric offsets of strings returns `TRUE`.

Examples

Example #1 A simple empty / isset comparison.


<?php
$var = 0;

// Evaluates to true because $var is empty
if (empty($var)) {
    echo '$var is either 0, empty, or not set at all';
}

// Evaluates as true because $var is set
if (isset($var)) {
    echo '$var is set even though it is empty';
}
?>

Example #2 empty on String Offsets

PHP 5.4 changes how empty behaves when passed string offsets.


<?php
$expected_array_got_string = 'somestring';
var_dump(empty($expected_array_got_string['some_key']));
var_dump(empty($expected_array_got_string[0]));
var_dump(empty($expected_array_got_string['0']));
var_dump(empty($expected_array_got_string[0.5]));
var_dump(empty($expected_array_got_string['0.5']));
var_dump(empty($expected_array_got_string['0 Mostel']));
?>

Output of the above example in PHP 5.3:

bool(false)
bool(false)
bool(false)
bool(false)
bool(false)
bool(false)

Output of the above example in PHP 5.4:

bool(true)
bool(false)
bool(false)
bool(false)
bool(true)
bool(true)

Notes

Note: Because this is a language construct and not a function, it cannot be called using variable functions.

Note:
When using empty on inaccessible object properties, the __isset() overloading method will be called, if declared.

empty