if ( ( $variables['var2'] !== 'cbactivity' ) || ( ! $variables['var4'] ) || ( ! isset( $variables['var4']['action'] ) ) ) {
	return;
}

// Check if the URL contains an action and that it is an activity URL
$queryAction					=	( $variables['var4']['action'] ?? '' );

if ( $queryAction !== 'activity' ) {
	return;
}

// Check if the URL contains a function and if not default to show function
$queryFunc						=	( $variables['var4']['func'] ?? 'show' );

if ( $queryFunc !== 'show' ) {
	return;
}

// Check if the URL contains an ID
$queryId						=	(int) ( $variables['var4']['id'] ?? 0 );

if ( ! $queryId ) {
	return;
}

// LOAD ACTIVITY OBJECT HERE BASED OFF $queryId

// IF NOT FOUND RETURN HERE TO ABORT REWRITE

// IF FOUND CHECK IF IT HAS WHATEVER DATA YOU WANT IN THE URL

// IF SAID DATA IS MISSING RETURN HERE TO ABORT REWRITE

// NOW BUILD THE URL SEGMENTS HERE LIKE THE FOLLOWING EXAMPLE
$variables['var3'][]			=	$queryAction;
$variables['var3'][]			=	$queryFunc;
$variables['var3'][]			=	$queryId;

// Remove the old query parameters above since we're converting this to segments
unset( $variables['var4']['action'] );
unset( $variables['var4']['func'] );
unset( $variables['var4']['id'] );