EOT;
$DOM = new DOMDocument();
$DOM->loadHTML($html);
$xpath = new DomXpath($DOM);
$prices = $xpath->query('//*[contains(concat(" ", normalize-space(@class), " "), "priceText ")]');
$percent = 20.0 / 100.0; // 20%
foreach($prices as $price){
$value = $price->nodeValue;
$floatValue = floatval($value);
$finalValue = $floatValue - ($percent * $floatValue);
echo sprintf("O valor %.2f teve um desconto de %.2f. Valor com desconto %.2f\r\n", $floatValue,
$percent, $finalValue);
}