getCustomVariable() public method

If scope is 'visit', it will attempt to read the value set in the first party cookie created by Piwik Tracker ($_COOKIE array).
public getCustomVariable ( integer $id, string $scope = 'visit' ) : mixed
$id integer Custom Variable integer index to fetch from cookie. Should be a value from 1 to 5
$scope string Custom variable scope. Possible values: visit, page, event
return mixed An array with this format: array( 0 => CustomVariableName, 1 => CustomVariableValue ) or false
 /**
  * Test setting/getting the first party cookie via the PHP Tracking Client
  * @param $t
  */
 private function testFirstPartyCookies(PiwikTracker $t)
 {
     $domainHash = $this->getFirstPartyCookieDomainHash();
     $idCookieName = '_pk_id_1_' . $domainHash;
     $refCookieName = '_pk_ref_1_' . $domainHash;
     $customVarCookieName = '_pk_cvar_1_' . $domainHash;
     $viewts = '1302307497';
     $uuid = 'ca0afe7b6b692ff5';
     $_COOKIE[$idCookieName] = $uuid . '.1302307497.1.' . $viewts . '.1302307497';
     $_COOKIE[$refCookieName] = '["YEAH","RIGHT!",1302307497,"http://referrer.example.org/page/sub?query=test&test2=test3"]';
     $_COOKIE[$customVarCookieName] = '{"1":["VAR 1 set, var 2 not set","yes"],"3":["var 3 set","yes!!!!"]}';
     // test loading 'id' cookie
     self::assertContains("_viewts=" . $viewts, $t->getUrlTrackPageView());
     self::assertEquals($uuid, $t->getVisitorId());
     self::assertEquals($t->getAttributionInfo(), $_COOKIE[$refCookieName]);
     self::assertEquals(array("VAR 1 set, var 2 not set", "yes"), $t->getCustomVariable(1));
     self::assertFalse($t->getCustomVariable(2));
     self::assertEquals(array("var 3 set", "yes!!!!"), $t->getCustomVariable(3));
     self::assertFalse($t->getCustomVariable(4));
     self::assertFalse($t->getCustomVariable(5));
     self::assertFalse($t->getCustomVariable(6));
     self::assertFalse($t->getCustomVariable(-1));
     unset($_COOKIE[$idCookieName]);
     unset($_COOKIE[$refCookieName]);
     unset($_COOKIE[$customVarCookieName]);
 }