What are the consequences of not updating PHP function calls to match newer versions?

If PHP function calls are not updated to match newer versions, it can lead to deprecated function warnings or errors, which may cause the code to break or not function properly. To solve this issue, it is important to update the function calls to use the correct syntax and parameters as specified in the latest PHP documentation.

// Deprecated function call
$oldResult = mysql_query($query);

// Updated function call
$newResult = mysqli_query($connection, $query);