Get PHP script to output result when completed - browser continues running - php

Question

I have a PHP script that writes data to files in batches of 5000 table rows. When all the rows have been written to file(s) it should output the time taken to run the script. Instead what is happening is the script appears to be continually running on the browser and the output never appears but the file(s) exist, meaning the script has run. This only happens with large amounts of data. Any suggestions?
$startTime = time();
$ID = '123';
$productBatchLimit = 5000;
$products = new Products();
$countProds = $products->countShopKeeperProducts();
//limit the amount of products
//if ($countProds > $productBatchLimit){$countProds = $productBatchLimit; }
$counter = 1;
for ($i = 0; $i < $countProds; $i += $productBatchLimit) {
$xml_file = 'xml/products/'. $ID . '_'. $counter .'.xml';
$xml = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n";
$xml .= "<products>\n";
//create new file
$fh = fopen($xml_file, 'a');
fwrite($fh, $xml);
$limit = $productBatchLimit*$counter;
$prodList = $products->getProducts($i, $limit);
foreach ($prodList as $prod ){
$xml = "<product>\n";
foreach ($prod as $key => $value){
$value = functions::xml_entities($value);
$xml .= "<{$key}>{$value}</{$key}>\n";
}
$xml .= "</product>\n";
fwrite($fh, $xml);
}
$counter++;
fwrite($fh, '</products>');
fclose($fh);
}
//check to see when XML is fully formed
$validxml = XMLReader::open($xml_file);
$validxml->setParserProperty(XMLReader::VALIDATE, true);
if ($validxml->isValid()==true){
$endTime = time();
echo "Total time to generate results: ".($endTime - $startTime)." seconds. \n";
} else {
echo "Problem saving Products XML.\n";
}