php script to Bulk Update AMP cache to clear AMP urls

clear_amp_cache.php

<?php

function urlsafe_b64encode($string) {
    return str_replace(array('+','/','='),array('-','_',''), base64_encode($string));
}


$ampBaseUrl="https://www-example-com-au.cdn.ampproject.org";

$file = fopen("urls.txt", "r") or exit("Unable to open file!");
//Output a line of the file until the end is reached
while(!feof($file))
  {

//$signatureUrl = '/update-cache/c/s/www.example.com.au/some-url.html?amp=1&amp_action=flush&amp_ts='.time();
  $signatureUrl =  trim(fgets($file)).time();

// opening the private key
$pkeyid = openssl_pkey_get_private("file://private-key.pem");

// generating the signature
openssl_sign($signatureUrl, $signature, $pkeyid, OPENSSL_ALGO_SHA256);

// urlsafe base64 encoding
$signature = urlsafe_b64encode($signature);

// final url for updating
$ampUrl = $ampBaseUrl.$signatureUrl."&amp_url_signature=".$signature;

echo $ampUrl . "\n";
$curl = curl_init();
curl_setopt($curl, CURLOPT_URL, $ampUrl);
$result = curl_exec($curl);
echo "\n";

  }
fclose($file);
?>