What is the difference between ereg_replace and preg_replace in PHP?

The main difference between ereg_replace and preg_replace in PHP is that ereg_replace uses POSIX extended regular expressions while preg_replace uses Perl-compatible regular expressions. POSIX extended regular expressions are simpler and less powerful than Perl-compatible regular expressions. Therefore, if you need more advanced regular expression features, it is recommended to use preg_replace.

// Using preg_replace to replace a pattern in a string
$string = "Hello, World!";
$new_string = preg_replace("/Hello/", "Hi", $string);
echo $new_string;