Namespace missing - yii2-advanced-app

Question

I have following class in folder frontend/migrations
use yii\db\Schema;
class m170727_180101_Bewerbungen extends \yii\db\Migration
{
public function safeUp()
{
$tableOptions = null;
if ($this->db->driverName === 'mysql') {
$tableOptions = 'CHARACTER SET utf8 COLLATE utf8_general_ci ENGINE=InnoDB';
}
$this->createTable('bewerbungen', [
'bew_id' => $this->primaryKey(),
'datum' => $this->date()->notNull(),
'firma' => $this->string(100)->notNull(),
'rechtsart' => $this->integer(11),
'stadt' => $this->string(100)->notNull(),
'plz' => $this->integer(11)->notNull(),
'strasse_nr' => $this->string(100),
'ansprech_person' => $this->string(100),
'email' => $this->string(50)->notNull(),
'feedback' => $this->integer(11),
'bemerkungen' => $this->string(150),
'FOREIGN KEY ([[feedback]]) REFERENCES nachricht ([[id_message]]) ON DELETE CASCADE ON UPDATE CASCADE',
'FOREIGN KEY ([[rechtsart]]) REFERENCES rechtsform ([[id_recht]]) ON DELETE CASCADE ON UPDATE CASCADE',
], $tableOptions);
}
public function safeDown()
{
$this->dropTable('bewerbungen');
}
}
Each try to read out method safeUp() throws out error:
Unable to find 'frontend\migrations\m170727_180101_Bewerbungen' in file: E:\xampp\htdocs\Yii2_Mail/frontend/migrations/m170727_180101_Bewerbungen.php. Namespace missing?**
Here is my script:
namespace frontend\migrations; ...
$connect=new m170727_180101_Bewerbungen();
$connect->safeUp(); ...
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What the hell is that?
The same error using like this:
$connect=new \frontend\migrations\m170727_180101_Bewerbungen();
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Answer 1

Try using the full path
$connect=new \frontend\migration\m170727_180101_Bewerbungen();

Answer 2

You have got this error because there is no namespace in your file so autoloader can not find it.
But this is not the real problem here - you are not using Yii 2 migration properly. Follow the Yii2 Migration Guide.
In addition, since you placed this migration in frontend you might want to take a look at Namespaced Migrations to actually add namespace there and to run it properly.