> legacy apps that were built in the PHP 5.2 or even PHP 4 days, be afraid. Be very afraid BS. Most PHP4 code runs just fine, as do PHP5 code. Almost no one us

> legacy apps that were built in the PHP 5.2 or even PHP 4 days, be afraid. Be very afraid BS. Most PHP4 code runs just fine, as do PHP5 code. Almost no one used object oriented code in PHP4 days (it was slow!), so the incompatible changes aren't a problem. And all you need to do is to search and replace some function names like mysql_* to mysqli_*. Most old code bases from PHP4 days also didn't rely on frameworks at all and were completely written from scratch or copy&pasted together - actually an advantage in this case. Upgrading an old Python or Ruby code from 1.x/2.x days is a lot of more work (as it always includes upgrading to a recent framework version) than upgrading from PHP4 or PHP5 to PHP7.