How can the use of outdated PHP functions like eregi be replaced with more modern and secure alternatives like preg in the context of recaptcha implementation?

The outdated PHP function eregi is deprecated and insecure, so it should be replaced with the more modern and secure alternative preg_match when implementing reCAPTCHA. To do this, you can simply modify the existing code that uses eregi to use preg_match instead.

// Old code using eregi
if (eregi("pattern", $string)) {
    // do something
}

// Updated code using preg_match
if (preg_match("/pattern/i", $string)) {
    // do something
}