php - Is it possible to Delete a value passed to a method, from within the method -

say have method (which in particular case static method), , method works on given value. once completed there way can automatically in code, delete variable (rather function copy).

i suspect i've read not possible, there no clear declarations of such searching has found.

an example case:

static method:

public static function checkkey($keyvalue = null) {     if(!is_null($keyvalue) && !empty($keyvalue)) {         if($_session['keyvalue'] == $keyvalue) {             unset($keyvalue,$_session['keyvalue']);             return true;         }         unset($keyvalue,$_session['keyvalue']);         return false;     }     return false; } 

usage:

$valuetobechecked = "i want value unset within function" //php page code  abstractclass::checkkey($valuetobechecked); 

is there way method checkkey above can delete value of $valuetobechecked from within method checkkey?

the fact it's static method shouldn't critical, it's more shape of there way function can delete value set outside funtion/method, when passed variable parameter?

i realise possible if whole thing wrapped in class , variable saved class level variable (unset($this->var)), i'm curious if there's ability "reach" variables outside scope such

public static function checkkey($keyvalue = null) {     unset(\$keyvalue); } 

i have limited experience namespacing that's best guess if possible, how go it.

simplified equiviliant outcome:

what i'm trying reach action, entirely within method:

$valuetobechecked = "something" abstractclass::checkkey($valuetobechecked); unset($valuetobechecked); 

you cannot unset variable within function , have effect propagate. per manual:

if variable passed reference unset() inside of function, local variable destroyed. variable in calling environment retain same value before unset() called.

however, can equivalent behavior through pass-by-reference , setting null:

function kill(&$value) {     $value = null; }  var_dump($x); // null $x = 'foo'; var_dump($x); // 'foo' kill($x); var_dump($x); // null 

this works because, in php, there's no distinction made between symbol doesn't exist , symbol exists null value.