Fields.php

<?php namespace Studiobanks;

class Fields
{
    public static function createEntity() {
        // $field = entity_create('field_entity', [
        //     'id' => 'field_text_slug',
        //     'name' => 'field_text_slug',
        //     'entity_type' => 'node',
        //     'type' => 'text',
        //     'cardinality' => 1
        // ]);

        // $field->save();

        // entity_create('field_instance', [
        //     'field_name' => 'field_text_slug',
        //     'entity_type' => 'node',
        //     'field_uuid' => 'node',
        //     'bundle' => 'blog_post'
        // ])->save();

        $node = \Drupal::entityManager()
            ->getStorageController('node')
            ->create([
                'title' => 'Some node',
                'bundle' => 'blog_post',
            ]);
        $test = true;
    }

    public static function createCategorySlugTable()
    {
        db_create_table('category_slug', [
            'fields' => [
                'category' => [
                    'description' => 'Category',
                    'type' => 'varchar',
                    'length' => 255,
                    'not null' => FALSE,
                    'default' => '',
                ],
                'category_slug' => [
                    'description' => 'Category Slug',
                    'type' => 'varchar',
                    'length' => 255,
                    'not null' => FALSE,
                    'default' => '',
                ],
            ]
        ]);

        echo 'Category Slug Field Created' . "\n";
    }
}