Cam someone help me in Html Code Validations?

Question

I'm using a PHP for server side database.

Answer 1

html validation as in improper tags and issues. if so, w3c has a validator to show you issues.
https://validator.w3.org
copy and paste your raw html there. raw as in before the browser parses it.
if you mean to validate it before you save it then mayhaps there is a library for that. this SO post seems to mention one that interfaces with w3c validator for php
https://stackoverflow.com/questions/1349372/php-based-html-validator

Answer 2

The textbox shouldn't accept two or more spacings + multiple dots (.)

The accepted value or data for example shouldn't be repeated.

Answer 3

I think html validations will not helpful for you Front-end validation through JavaScript or JS frameworks /libraries (React, Vue.js, Angular, JQuery) easier and much better way

Answer 4

How can I put it on JQuery sir?

Answer 5

Makki Balindong
https://www.google.com/amp/s/www.geeksforgeeks.org/form-validation-using-jquery/amp/