What potential issues can arise when updating a website from Typo3 4.xx to Typo3 7.xx?

One potential issue when updating a website from Typo3 4.xx to Typo3 7.xx is deprecated functions and methods that may no longer be supported in the newer version. To solve this, you will need to update your code to use the new functions and methods provided in Typo3 7.xx.

// Deprecated function in Typo3 4.xx
// $oldResult = mysql_query($query);

// Updated code for Typo3 7.xx
$newResult = $GLOBALS['TYPO3_DB']->sql_query($query);