<?php
$carpilan = null;
$carpan = null;
function vir2nok($data) {
	return str_replace(",",".",$data);
}
if ($_POST) {
	$carpilan = vir2nok($_POST["carpilan"]);
	$carpan = vir2nok($_POST["carpan"]);
	if (is_numeric($carpilan) && is_numeric($carpan)) {
		$sonuc = $carpilan * $carpan;
		echo $carpilan." x ".$carpan." = ".$sonuc."<hr>";
	}
}
?>
<form action="" method="post">
	<input type="text" name="carpilan" placeholder="Çarpılan" value="<?php echo $carpilan; ?>">
	<input type="text" name="carpan" placeholder="Çarpan" value="<?php echo $carpan; ?>">
	<input type="submit" name="gonder">
</form>