What are the potential pitfalls of using regular expressions for searching and replacing in PHP variables?

One potential pitfall of using regular expressions for searching and replacing in PHP variables is that complex regex patterns can be difficult to debug and maintain. To avoid this issue, it's recommended to use PHP's built-in string functions like `str_replace()` or `preg_replace_callback()` for simpler search and replace operations.

// Using str_replace() for simple search and replace
$originalString = "Hello, world!";
$newString = str_replace("world", "PHP", $originalString);
echo $newString;