How to fix str_replce Deprecated Functionality error in magento 2.4.4 - PHP 8.1

That error indicates somewhere in your code passing null to the third parameter when calling a PHP function that is deprecated in PHP 8.1.

Assume you have below code:

return sprintf(
    $path,
    str_replace('methods_', '', $method)
);

The type of the third parameter should be changed to string if it is null. So the fixed code looks like the below:

return sprintf(
    $path,
    str_replace('methods_', '', $method ?? '')
);

The solution for your code:

$fromDate = date("Y-m-d",strtotime(str_replace("/", "-", $helper->getNewYearBallFromDate() ?? '')));
$toDate  = date("Y-m-d",strtotime(str_replace("/", "-", $helper->getNewYearBallToDate() ?? '')));