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PHP

Determine whether a variable is empty


empty

(PHP 4, PHP 5)

emptyDetermine whether a variable is empty

Description

bool empty ( mixed $var )

Determine whether a variable is considered to be empty.

Parameters

var

Variable to be checked

Note:

empty() only checks variables as anything else will result in a parse error. In other words, the following will not work: empty(trim($name)).

empty() is the opposite of (boolean) var, except that no warning is generated when the variable is not set.

Return Values

Returns FALSE if var has a non-empty and non-zero value.

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 $var; (a variable declared, but without a value in a class)

Changelog

Version Description
5.4.0

Checking non-numeric offsets of strings returns TRUE.

5.0.0

Objects with no properties are no longer considered empty.

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.

See Also



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