What are some common pitfalls when upgrading PHP versions, and how can they be avoided?

One common pitfall when upgrading PHP versions is deprecated functions or features that are no longer supported in the new version. To avoid this, thoroughly review the PHP documentation for deprecated features and update your code accordingly. Additionally, ensure all third-party libraries and frameworks are compatible with the new PHP version before upgrading.

// Example code to avoid using deprecated function: ereg_replace()
// Replace with preg_replace()

// Deprecated function
$string = "Hello, World!";
$pattern = "Hello";
$replacement = "Hi";
$new_string = ereg_replace($pattern, $replacement, $string);

// Updated code using preg_replace
$new_string = preg_replace("/$pattern/", $replacement, $string);