$connection->update('key_value')
->fields([
- 'value' => serialize(array_merge($existing_blocks, ['block.block.testfor2354889', 'block.block.secondtestfor2354889', 'block.block.thirdtestfor2354889']))
+ 'value' => serialize(array_merge($existing_blocks, ['block.block.testfor2354889', 'block.block.secondtestfor2354889', 'block.block.thirdtestfor2354889'])),
])
->condition('collection', 'config.entity.key_store.block')
->condition('name', 'theme:bartik')