Документация PHP
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empty
(PHP 4, PHP 5)
empty — Determine whether a variable is empty
Описание
bool empty ( mixed $var )
Determine whether a variable is considered to be empty.
Список параметров
- var
-
Variable to be checked
Замечание: empty() only checks variables as anything else will result in a parse error. In other words, the following will not work: empty(trim($name)).
empty() is the opposite of (boolean) var, except that no warning is generated when the variable is not set.
Возвращаемые значения
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 as a string)
- NULL
- FALSE
- array() (an empty array)
- var $var; (a variable declared, but without a value in a class)
Список изменений
| Версия | Описание |
|---|---|
| PHP 5 |
As of PHP 5, objects with no properties are no longer considered empty. |
| PHP 4 |
As of PHP 4, The string value "0" is considered empty. |
Примеры
Пример #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';
}
?>
Примечания
Замечание: Поскольку это языковая конструкция, а не функция, она не может вызываться при помощи переменных функций
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