XML: Crear un fichero XML desde PHP

$fp = fopen("fichero1.xml", "w+");
fputs($fp, '<?xml version="1.0" encoding="UTF-8"?>'.PHP_EOL);
fputs($fp, '
<urlset
xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"
                xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation="http://www.sitemaps.org/schemas/sitemap/0.9
            http://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd">'.PHP_EOL);

foreach ($arrLinks as $key =>$valor) {
$cadena = "<url>".PHP_EOL."<loc>".$key."</loc>".PHP_EOL."</url>";
fputs($fp, $cadena.PHP_EOL);
}
fputs($fp, "</urlset>".PHP_EOL);
fclose($fp);