Form submission not working properly from wordpress page - php

Question

I am trying to make an insert form directly inside wordpress post, the code is working partly fine i.e. it is adding blank row in "test" table in "webdatabase" with every submission but not adding any value in name and rollno column, it is also not displaying any error.
Please help so that value submitted through form can be inserted in to "test" table, thanks in advance.
My form with php code is as under:
<form action="http://localhost/wordpress" method="POST">
Name:<br><input type="text" name="name" value=""><br>
Roll No:<br><input type="text" name="rollno" value=""><br><br>
<input type="submit" value="Submit">
</form>
<?php
$testname = $_POST['name'];
$testrollno = $_POST['rollno'];
$conn = new mysqli("localhost","root", "","webdatabase");
$sql = "INSERT INTO test (name,rollno) VALUES (' " . $testname . " ', '" . $testrollno . "')";
mysqli_query($conn, $sql);
$conn->close();
?>
My table structure in mysql database is shown as under:
Column Type
ID int(15)
name varchar(20)
rollno varchar(20)

Answer 1

You can use the “isset” function on any variable to determine if it has been set or not. You can use this function on the $_POST array to determine if the variable was posted or not. This is often applied to the submit button value, so
The HTML will be;
<form action="http://localhost/wordpress" method="POST">
Name:<br><input type="text" name="name" value=""><br>
Roll No:<br><input type="text" name="rollno" value=""><br><br>
<input type="submit" name="action" value="Submit">
</form>
and PHP will be;
<?php
if (isset($_POST['action'])) {
$testname = mysqli_real_escape_string($_POST['name']);
$testrollno = mysqli_real_escape_string($_POST['rollno']);
$conn = new mysqli("localhost","root", "","webdatabase");
$sql = "INSERT INTO test (name,rollno) VALUES (' " . $testname . " ', '" . $testrollno . "')";
mysqli_query($conn, $sql);
$conn->close();
}
?>

Answer 2

Since you are using WordPress, you should use the WordPress DB API. https://codex.wordpress.org/Class_Reference/wpdb
Complete code:
<form action="http://localhost/wordpress" method="POST">
Name:<br /><input type="text" name="name" value=""><br />
Roll No:<br /><input type="text" name="rollno" value="" /><br /><br />
<input type="submit" value="Submit">
</form>
<?php
if ($_SERVER['REQUEST_METHOD'] == 'POST') {
$wpdb->insert('test', array('name' => $_POST['name'], 'rollno' => $_POST['rollno']));
}
Note: above code is untested