How can I use $_POST to update data in a database?

In update.php, you can update the database record:

<?php
$servername = "localhost";
$username = "root";
$password = "";
$dbname = "test_db";

// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);

// Check connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}

if ($_SERVER["REQUEST_METHOD"] === "POST") {
    $id = $_POST["id"];
    $name = $_POST["name"];
    
    // Prepare and bind
    $stmt = $conn->prepare("UPDATE users SET name = ? WHERE id = ?");
    $stmt->bind_param("si", $name, $id);

    // Execute the query
    if ($stmt->execute()) {
        echo "Record updated successfully";
    } else {
        echo "Error updating record: " . $conn->error;
    }

    $stmt->close();
}
$conn->close();
?>

This script uses a prepared statement to update a record securely. Prepared statements help prevent SQL injection by separating SQL code from data.