Usefull PHP Command line Switches

$f = empty($_GET['f']) ? "" : $_GET['f'];

if( file_exists($f ) ){
    $f = realpath($f);
    $cmd = " php -s $f ";
    #echo $cmd;
    exec($cmd, $op);
    echo implode("\r\n", $op) ;

}else{
    echo "Requested file not found : $f ";
}