How can one ensure compatibility when upgrading PHP versions for existing codebases?

When upgrading PHP versions for existing codebases, it is important to ensure compatibility by checking for deprecated functions, outdated syntax, and potential breaking changes. One way to do this is by using tools like PHP Compatibility Checker to identify any issues before upgrading. Additionally, testing the codebase thoroughly after the upgrade can help catch any compatibility issues that may have been missed.

// Example code snippet for checking compatibility before upgrading PHP version
require 'vendor/autoload.php';

use PhpParser\ParserFactory;
use PhpParser\NodeTraverser;
use PhpParser\NodeVisitor\NameResolver;
use PhpParser\Error;

$parser = (new ParserFactory)->create(ParserFactory::PREFER_PHP7);
$traverser = new NodeTraverser;
$traverser->addVisitor(new NameResolver);