What are the common issues faced when transitioning from PHP version 4 to version 7.2?

Issue: One common issue when transitioning from PHP version 4 to version 7.2 is the removal of deprecated functions and features. This includes functions like split() and ereg(), which have been removed in PHP 7. To solve this issue, you need to update your code to use modern equivalents like explode() and preg_match(). Code snippet:

// PHP 4 code using split()
$pieces = split(",", $string);

// Updated PHP 7.2 code using explode()
$pieces = explode(",", $string);