What potential issues can arise when upgrading from PHP 7.0 to 7.1 in a system with collapsible navigation?

When upgrading from PHP 7.0 to 7.1 in a system with collapsible navigation, potential issues can arise due to changes in the PHP syntax and deprecated functions. To solve this, ensure that all deprecated functions are replaced with their updated equivalents and update any syntax that may have changed between PHP versions. Additionally, check for any compatibility issues with third-party plugins or libraries that may need updates.

// Example of updating deprecated function in PHP 7.0 to PHP 7.1
// Deprecated function in PHP 7.0
$oldArray = array(1, 2, 3);

// Updated equivalent in PHP 7.1
$newArray = [1, 2, 3];

// Use the updated syntax to avoid issues in PHP 7.1