(PHP 4, PHP 5)
empty — Determine whether a variable is empty
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.
var
Variable to be checked
Informacja:
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.
Returns FALSE if var exists and has a non-empty, non-zero value.
Otherwise returns TRUE.
The following things are considered to be empty:
NULLFALSE
| Wersja | Opis |
|---|---|
| 5.5.0 |
empty() now supports expressions, rather than only variables. |
| 5.4.0 |
Checking non-numeric offsets of strings returns |
| 5.0.0 |
Objects with no properties are no longer considered empty. |
Przykład #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';
}
?>
Przykład #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)
Informacja: Ponieważ jest to element składni języka a nie funkcja, nie może być on wywoływany używając zmiennych funkcji
Informacja:
When using empty() on inaccessible object properties, the __isset() overloading method will be called, if declared.