how to persist values in form after incorrect input html code example

Example 1: how to mantain text in form after error php

<input type="text" id="name" name="name" value="<?php echo isset($_POST["name"]) ? $_POST["name"] : ''; ?>">

Example 2: input show validation message

// Validate emai

var applicationForm = document.getElementById("applicationForm");    
if (applicationForm.checkValidity()) {
  applicationForm.submit();
} else {
  applicationForm.reportValidity();
}