Model (example)

<?php

namespace app\models;

use Yii;
use yii\web\UploadedFile;

/**
 * This is the model class for table "contactperson".
 *
 * @property int $id
 * @property int $account_id
 * @property int|null $salutation
 * @property string|null $name
 * @property string|null $role
 * @property string|null $image_filename
 * @property string|null $phone
 * @property string|null $phone_mobile
 * @property string|null $email
 *
 * @property Account $account
 * @property Group $group
 */
class Contactperson extends \yii\db\ActiveRecord
{
    /* @var UploadedFile */
    public $image;
    /* @var bool */
    public $uploaded = false;

    const SCENARIO_UPLOAD_ONLY = "upload";
    const SCENARIO_SAVE = "save";

    public function scenarios()
    {
        $scenarios = parent::scenarios();
        $scenarios[self::SCENARIO_UPLOAD_ONLY] = ['image', 'image_filename'];
        $scenarios[self::SCENARIO_SAVE] = ['account_id', 'salutation', 'name', 'role', 'image_filename', 'phone', 'phone_mobile', 'email'];
        return $scenarios;
    }

    /**
     * {@inheritdoc}
     */
    public static function tableName()
    {
        return 'contactperson';
    }

    /**
     * {@inheritdoc}
     */
    public function rules()
    {
        return [
            ['image', 'image', 'skipOnEmpty' => true, 'extensions' => 'png, jpg, jpeg'],

            [['account_id', 'name', 'role', 'email'], 'required', 'on' => self::SCENARIO_SAVE],
            [['account_id', 'salutation'], 'integer'],
            [['name', 'role'], 'string', 'max' => 128],
            [['image_filename'], 'string', 'max' => 255],
            [['phone', 'phone_mobile'], 'string', 'max' => 32],
            [['email'], 'string', 'max' => 96],
            ['email', 'email'],
            [['account_id'], 'exist', 'skipOnError' => false, 'targetClass' => Account::class, 'targetAttribute' => ['account_id' => 'id']],
            //['account_id', 'default', 'value' => Yii::$app->account->data->id],
        ];
    }


    /**
     * @return \yii\db\ActiveQuery
     */
    public function getAccount()
    {
        return $this->hasOne(Account::class, ['id' => 'account_id']);
    }

    /**
     * @return \yii\db\ActiveQuery
     * @throws \yii\base\InvalidConfigException
     */
    public function getGroup()
    {
        return $this->hasOne(Group::class, ['id' => 'group_id'])->viaTable('group_contactperson', ['contactperson_id'=>'id']);
    }

    public function upload(){
        if( $this->validate() ){
            $newFilename = $this->image->baseName.'.'.$this->image->extension;
            //delete old image if it has not the same filename
            if( !empty($this->image_filename) ){
                if( $this->image_filename !== $newFilename ){
                    unlink( Yii::getAlias('@webroot') .'/'.$this->account_id.'/uploads/'.$this->image_filename );
                }
            }

            $this->image->saveAs(Yii::getAlias('@webroot') .'/'.$this->account_id.'/uploads/'.$newFilename);
            //process image with IMAGINE to fit sizes
            //generate a small image
            $this->image_filename = $newFilename;
            $this->uploaded = true;
        }else{
            $this->uploaded = false;
        }
    }

    public function getImagePath(){
        if (!empty($this->image_filename)) {
            $profileImagePath = Yii::getAlias('@web') . '/' . $this->account_id . '/uploads/' . $this->image_filename;
        } else {
            $profileImagePath = '/img/default_contact_profileimage.png';
        }
        return $profileImagePath;
    }
}