PHP. Руководство по PHP. 2005

unset

(PHP 3, PHP4, PHP 5)unset -- Unset a given variable

Description

void unset (mixed var [, mixed var [, mixed ...]])

unset() destroys the specified variables. Note that in PHP 3, unset() will always return TRUE (actually, the integer value 1). In PHP4, however, unset() is no longer a true function: it is now a statement. As such no value is returned, and attempting to take the value of unset() results in a parse error.

Пример 1. unset() example


<?
//destroy a single variable
unset($foo);
//destroy a single element of an array
unset($bar['quux']);
//destroy more than one variable
unset($foo1, $foo2, $foo3);

?>

The behavior of unset() inside of a function can vary depending on what type of variable you are attempting to destroy.

If a globalized variable is unset() inside of a function, only the local variable is destroyed. The variable in the calling environment will retain the same value as before unset() was called.


<?
function destroy_foo()
{
global $foo;
unset($foo);
}
$foo = 'bar';
destroy_foo();
echo $foo;

?>

Результат выполнения данного примера:

bar

If a variable that is PASSED BY REFERENCE is unset() inside of a function, only the local variable is destroyed. The variable in the calling environment will retain the same value as before unset() was called.


<?
function foo(&$bar)
{
unset($bar);
$bar = "blah";
}
$bar = 'something';
echo "$bar\n";
foo($bar);
echo "$bar\n";

?>

Результат выполнения данного примера:

something

If a static variable is unset() inside of a function, unset() destroys the variable and all its references.


<?
function foo()
{
static $a;
$a++;
echo "$a\n";
unset($a);
}
foo();
foo();
foo();

?>

Результат выполнения данного примера:

If you would like to unset() a global variable inside of a function, you can use the $GLOBALS array to do so:


<?
function foo()
{
unset($GLOBALS['bar']);
}
$bar = "something";
foo();

?>

Замечание:Поскольку это языковая

конструкция, а не функция, она не может вызываться при помощи

переменных функций

See also isset(), empty(), and array_splice().

unserialize

var_dump

Отвечу на любые вопросы. С уважением, Дмитрий Владимирович.

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