Sabin cod

// html form
<form action="post.php" method="post">
    Text: <input type="text" name="data1" />
    Text: <input type="text" name="data2" />
    Text: <input type="text" name="data3" />
    Text: <input type="text" name="data4" />
    <input type="button" name="submit" value="Submit">
</form>


// db.php content
$link = mysqli_connect("127.0.0.1", "my_user", "my_password", "my_db");

// post.php
require 'db.php';
require 'sendpost.php';

if(isset($_POST['submit'])) {
    insertToDatabase([
        'data1' => $_POST['data1'],
        'data2' => $_POST['data2'],
        'data3' => $_POST['data3'],
        'data4' => $_POST['data4'],
    ]);
}

// sendpost.php
require 'db.php';

function insertToDatabase(array $postData) {
    global $link;
    if(!empty($postData) && is_array($postData) ) return false;
    $stmp = mysqli_query($link, 'INSERT INTO `table.name` (`data1`, `data2`, `data3`, `data4`) VALUES ($postData['data1'], $postData['data2'], $postData['data3'], $postData['data4'])');
    mysqli_close($link);
    endif;
}

// getdata.php
require 'db.php';
$result = mysqli_query($link, "SELECT * FROM `table.name`");
print_r($result); // return [0 => [0 => '', 1 => '', 2 => '', 3 => '']]