Yii2 Check if table exists in migration - php

Question

I have created a migration, whichi should create tables for my database, and insert default admin user.
<?php
//use Yii;
use yii\db\Migration;
use yii\db\Schema;
/**
* Class m180616_200856_create_tables
*/
require_once( __DIR__.'/../config.php');
class m180616_200856_create_tables extends Migration
{
public function up()
{
if (Yii::$app->db->schema->getTable("users",true)===null) {
$this->createTable('users', [
'id' => $this->primaryKey(),
'username' => $this->string(),
'password' => $this->string(),
'authKey' => $this->string(),
'accessToken' => $this->string()
]);
$this->insert('users',array(
'username'=> SUPERUSER_LOGIN,
'password' => md5(SUPERUSER_PASS ),
'authKey' => 'key',
'accessToken' => ''
));
}
}
public function down()
{
echo "m180616_200856_create_tables cannot be reverted.\n";
return false;
}
}
When i run this migration, i get the error:
*** applying m180616_200856_create_tables
Exception 'yii\base\UnknownMethodException' with message 'Calling unknown method: yii\db\mysql\Schema::getTable()'
If i include use Yii i get the error:
*** applying m180616_200856_create_tables
PHP Warning 'yii\base\ErrorException' with message 'The use statement with non-compound name 'Yii' has no effect'
So it seems i cannot use Yii namespace inside migration, how can i check if table exists?

Answer 1

In migration you can check if table does not exist in this way:
$tableName = $this->db->tablePrefix . 'users';
if ($this->db->getTableSchema($tableName, true) === null) {
It will usually work the same as:
$tableName = Yii::$app->db->tablePrefix . 'users';
if (Yii::$app->db->getTableSchema($tableName, true) === null) {
And yes, you can use Yii in migrations, it just does not make any sense to import class from global namespace if you're already in global namespace.