Use the accept attribute to limit the upload type of HTML file, such as accept="image/*" only allows images, accept=".pdf" only allows PDF, accept=".doc,.docx,.pdf,.txt" allows multiple specified types, and can combine JavaScript to verify file types to improve user experience, but security verification must be performed on the server side, because the accept attribute is not secure and the browser supports are different, and it is only used to improve availability rather than replace server verification.

Answer: To implement password reset in Yii2, you need to add password_reset_token and expiration time fields, generate a unique token and send it to the user's mailbox, and allow the user to set a new password by verifying the validity of the token, and finally clean the expired token. The specific steps include: 1. Modify the database to add token fields; 2. Implement the generatePasswordResetToken method in the User model to generate a time stamped token and set an hour validity period; 3. Create a PasswordResetRequestForm form to process the request, find the user and send an email with a reset link; 4. Define the strength of the ResetPasswordForm model to verify the new password

EnableGiiinconfig/web.phpbyaddingthemoduleandsettingallowedIPs,thenaccesshttp://your-app-url/index.php?r=gii,useModelGeneratortocreatemodelsfromdatabasetables,anduseCRUDGeneratortogeneratecontrollersandviewsforfullCRUDoperations.

Answer: To handle file upload in Yii, you need to set the form enctype to multipart/form-data, use the UploadedFile class to get the file, verify the file type through the model verification rules, and save the file in the controller. Make sure that the upload directory can be written and renamed for security.

First,setupanHTMLformwithenctype="multipart/form-data"andmethod="post",thenaccessthefilevia$_FILESinPHP,validateitstype,size,anderrorstatus,moveitsecurelyusingmove_uploaded_file(),andfollowsecuritypracticeslikestoringoutsidewebroo

Yiiensuresdataintegritythroughtransactionmanagement,allowingrollbackonfailure.UsebeginTransaction()formanualcontrolortransaction()withaclosureforautomaticcommit/rollback.ActiveRecordmodelsautomaticallyparticipateintransactionswhenusingthesameconnecti

To create a custom widget, you need to inherit the yii\base\Widget class and implement the init() and run() methods. 2. Place the class file in the @app/widgets/ directory. 3. Use it in the view through widget() or begin() and end() syntax. 4. Complex output can render the view template through render() method. 5. Create resource packages when CSS/JS is required and register in run().

Answer: To implement search and filtering in Yii2, you need to create a search model and use ActiveDataProvider and GridView. First, create a ProductSearch class for Product, define rules and implement search methods, process parameters through load and validate, and add conditions with andFilterWhere; instantiate the search model in the controller and pass in the request parameters; build a search form in the view with ActiveForm, GridView displays data and sets filterModel; supports advanced functions such as date range and association query to ensure database index optimization performance.