// @see https://github.com/web-push-libs/web-push-php/blob/256a18b2a2411469c94943725fb6eccb9681bd75/src/Utils.php#L60-L62
$hexString = '04';
$hexString .= str_pad(bin2hex($pkey['ec']['x']), 64, '0', STR_PAD_LEFT);
$hexString .= str_pad(bin2hex($pkey['ec']['y']), 64, '0', STR_PAD_LEFT);
// @see https://github.com/web-push-libs/web-push-php/blob/256a18b2a2411469c94943725fb6eccb9681bd75/src/Utils.php#L60-L62
$hexString = '04';
$hexString .= str_pad(bin2hex($pkey['ec']['x']), 64, '0', STR_PAD_LEFT);
$hexString .= str_pad(bin2hex($pkey['ec']['y']), 64, '0', STR_PAD_LEFT);