mgc.longyilive.com/models/UploadExcel.php

<?php
namespace app\models;

use yii\base\Model;
use yii\web\UploadedFile;
use Yii;

class UploadExcel extends Model
{
    /**
     * @var UploadedFile
     */
    public $excel;

    public function rules()
    {
        return [
            [['excel'], 'file', 'skipOnEmpty' => false,'checkExtensionByMimeType'=>false, 'extensions' => 'csv,xls,xlsx'],
        ];
    }
    
    public function upload()
    {   
        if ($this->validate()) {
            $uploadDir = Yii::getAlias('@webroot') . Yii::getAlias('@web/uploads/'); 
            $file=time(). '.'.$this->excel->extension;
            $this->excel->saveAs($uploadDir. $file);
            return $uploadDir. $file;
        } else {
            return false;
        }
    }
    public function aa(){
        
    }
}