Save custom data to States

Reading State

A single value.

$val = \Drupal::state()->get('key');

Multiple key/value pairs.

$pairs = \Drupal::state()->getMultiple($keys);

Writing State

A single value.

\Drupal::state()->set('key','value');

Multiple values.

\Drupal::state()->setMultiple($keyvalues);

Removing State

Delete a value

\Drupal::state()->delete('key');