Replace all domain including subdomain name using PHP with Regex

preg_replace with regex.

$string = ' https://example.com, https://www.example.com, https://subdomain.example.com ';
$olddomain= "example.com";
$newdomain = "stackoverflow.com";

$output = preg_replace('#(https://(www\.)?)' . $olddomain. '#', '$1' . $newdomain, $string);

echo $output;

Output :

https://stackoverflow.com, https://www.stackoverflow.com, https://subdomain.example.com 

Without using Regex

$string = ' https://example.com, https://www.example.com, https://subdomain.example.com ';
$olddomain= "example.com";
$newdomain = "stackoverflow.com";

$parts = explode(",", $string);
$new_parts = [];

foreach ($parts as $part) {
    $new_parts[] = str_replace(['https://', 'http://', $olddomain], ['https://', 'http://', $newdomain], $part);
}

$output = implode(",", $new_parts);

echo $output;

Return

https://stackoverflow.com, https://www.stackoverflow.com, https://subdomain.example.com 

With Array and Regex

$string = ' https://example.com, https://www.example.com, https://subdomain.example.com ';
$olddomain = ["example.com", 'www\.'];
$newdomain = ["stackoverflow.com", ''];

$output = preg_replace('#https://(' . implode('|', $olddomain) . ')#', 'https://' . $newdomain[0], $string);
$output = preg_replace('#(' . $olddomain[1] . ')#', $newdomain[1], $output);

echo $output;