What potential issues can arise when migrating PHP files from one version to another?

One potential issue when migrating PHP files from one version to another is deprecated functions or features that may no longer be supported in the new version. To solve this, you should update your code to use the recommended alternatives provided by the new PHP version.

// Deprecated function in PHP 7.4
$deprecatedVar = implode(",", $array);

// Updated code using recommended alternative
$updatedVar = implode(",", $array);