PHP - unset() Function
Definition and Usage
The function unset() destroys the specified variables. 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.
Syntax
void unset ( mixed $var , mixed $vars )
Parameters
| Sr.No |
Parameter & Description |
| 1 |
var Mandatory.he variable to be unset. |
| 2 |
vars
Optional.Further variables. |
Return Values
This function does not return any value.
Dependencies
PHP 4 and above
Example
Following example demonstrates use of unset() function −
<?php
$a = "Welcome TutorialsPoint!";
echo "The value of 'a' before unset: " . $a . "<br>";
unset($a);
echo "The value of 'a' after unset: " . $a;
?>
Output
This will produce following result −
The value of 'a' before unset: Welcome TutorialsPoint!
The value of 'a' after unset:
Example
Following example demonstrates case when globalized variable is unset() inside of a function −
<?php
//globalized variable is unset() inside of a function
function destroy_a() {
global $a;
unset($a);
}
$a = 'Welcome TutorialsPoint!';
destroy_a();
echo "global unset inside function =".$a;
?>
Output
This will produce following result −
global unset inside function =Welcome TutorialsPoint!
Example
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. Following example demonstrates this −
<?php
function destroy_c($v) {
unset($c);
$c = "heloo";
}
$c = 'TutorialsPoint';
echo "$c<br>";
destroy_c($c);
echo "$c<br>";
?>
Output
This will not produce result −
TutorialsPoint
TutorialsPoint
php_variable_handling_functions.htm
