What potential issues can arise when upgrading from PHP 5 to PHP 7?

One potential issue when upgrading from PHP 5 to PHP 7 is deprecated functions and features that may no longer work in the new version. To solve this, you will need to update your code to use the recommended replacements for deprecated functions. 

// PHP 5 code using deprecated function
mysql_connect($server, $username, $password);

// PHP 7 code using recommended replacement
$mysqli = new mysqli($server, $username, $password);

Keywords

backward compatibility deprecated functions performance improvements error handling syntax changes

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