Create a simple Block programmatically

In drupal 8 block is part of the plugin system.

Step 1. Create a simple module like this.

Step 2. Create a foldr Block in your module

Ex: mymodule\Plugin\Block

Step 3. Create the block (Php Class in mymodule\Plugin\Block )

<?php

/**

 * @file

 * Contains \Drupal\mymodule\Plugin\Block\MyBlock .

 */

namespace Drupal\mymodule\Plugin\Block;

use Drupal\Core\Block\BlockBase;

/**

 * Provides the  Block 'MyBlock'.

 *

 * @Block(

 *   id = "mymodule_myblock",

 *   subject = @Translation("MyBlock"),

 *   admin_label = @Translation("MyBlock")

 * )

 */

class MyBlock extends BlockBase {

  /**

   * Implements \Drupal\block\BlockBase::blockBuild().

   */

  public function build() {

    $output = array();

    //Add this two linew if you want to create a dynamic contents block

    $output['cache']['#disabled'] = TRUE;

    $output['cache']['max_age']['#value'] = 0;

    $html = "";

    $html .= 'This is a programmatically created block  :  ' . date("H:i:s") ;

    $output[] = [      '#markup' => $html,    ];

    return $output;

  }

}

Step 4. Add your block to a page

• /admin/structure/block
• Place a Block (Where you want to place the block)
• Search your block 'MyBlock' and Place

See also to add a block programatically

$block_manager = \Drupal::service('plugin.manager.block');

$config = [];// You can hard code configuration or you load from settings.

$plugin_block = $block_manager->createInstance('system_breadcrumb_block', $config);

// If want to access check.

$access_result = $plugin_block->access(\Drupal::currentUser());

if (is_object($access_result) && $access_result->isForbidden() || is_bool($access_result) && !$access_result) {

  return [];

}

$render = $plugin_block->build();

// Add the cache tags/contexts.

\Drupal::service('renderer')->addCacheableDependency($render, $plugin_block);

return $render;