Clear the Cache using PHP

/////////////////////////////////////////// Clear Cache /////////////////////////////////////////////
function nocache(){
header('Cache-Control: no-cache, must-revalidate');
header('Pragma: no-cache');
$ExpStr = "Expires: " . gmdate("D, d M Y H:i: s ", time() ) . " GMT";
Header($ExpStr);
header('Cache-Control: public, no-cache');
}