How can PHP version changes affect the functionality of existing scripts?

PHP version changes can affect the functionality of existing scripts if deprecated functions or features are removed or altered in the new version. To solve this issue, it is important to update the code to use current PHP best practices and functions that are supported in the new version. This may involve rewriting certain parts of the script or using compatibility libraries to bridge the gap between the old and new PHP versions.

// Example of updating code to use current PHP best practices
// Before PHP 7.4
$sum = array_sum(array(1, 2, 3));

// After PHP 7.4
$sum = array_sum([1, 2, 3]);