unset

(unknown)

Description

unset() destroys the specified variables. Note that in PHP 3, unset() will always return TRUE (actually, the integer value 1). In PHP 4, 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.

Example 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;

bar

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

something
something

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

1
2
3

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