In PHP, what are the recommended best practices for converting specific substrings within a larger string to lowercase while preserving the original case of the first letter?

When converting specific substrings within a larger string to lowercase in PHP while preserving the original case of the first letter, a common approach is to use a combination of string manipulation functions like `substr`, `strtolower`, and `ucfirst`. By breaking down the string into parts, converting only the necessary substrings to lowercase, and then reconstructing the final string, you can achieve the desired outcome.

<?php
function preserveCase($string, $substring) {
    $lowercaseSubstring = strtolower($substring);
    $position = strpos($string, $substring);
    $firstLetter = substr($string, $position, 1);
    $firstLetter = strtolower($firstLetter);
    $firstLetter = ucfirst($firstLetter);
    
    return substr_replace($string, $firstLetter . substr($lowercaseSubstring, 1), $position, strlen($substring));
}

// Example usage
$string = "Hello World, How Are You?";
$substring = "world";
$result = preserveCase($string, $substring);
echo $result;
?>