What potential compatibility issues can arise when transitioning from an older PHP version to a newer one?

One potential compatibility issue when transitioning from an older PHP version to a newer one is deprecated functions or features that are no longer supported in the newer version. To solve this issue, you will need to update your code to use the recommended alternatives or refactor it to comply with the new PHP version's syntax and standards. 

// Deprecated function in PHP 7.4
// Using the deprecated function
$deprecatedVar = mysql_connect('localhost', 'username', 'password');

// Updated code using mysqli_connect
$updatedVar = mysqli_connect('localhost', 'username', 'password');

Keywords

PHP version backward compatibility deprecated functions syntax changes migration errors

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