What are some common reasons why JavaScript and jQuery may not function properly after upgrading to PHP 7.2?

One common reason why JavaScript and jQuery may not function properly after upgrading to PHP 7.2 is due to the removal of the 'register_globals' directive in PHP 7.2. This directive allowed PHP scripts to access variables directly from the global scope, which could cause conflicts with JavaScript and jQuery code. To solve this issue, you can use the $_POST or $_GET superglobals to access form data instead of relying on register_globals.

// Before PHP 7.2
$variable = $_POST['variable'];

// After PHP 7.2
$variable = $_POST['variable'] ?? '';