How to create your back end API using PHP to communicate with your flutter app?

<?php
/****
@author:Gcobani Mkontwana
@date:13/09/2023
@This application uses cors for allowing application to run.
@This app sign up users and sign them to the database table.
*/

header("Access-Control-Allow-Origin: *");
header("Content-Type: application/json; charset=UTF-8");

// Database connection
$servername = "localhost";
$username = "agile_log_admin";
$password = "*****";
$dbname = "agile_logistix_mobile";

try {
    $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

    // Handle POST data
    $data = json_decode(file_get_contents("php://input"));

    $username = $data->username;
    $email = $data->email;
    $password = $data->password;

    // Perform the database query (replace 'users_registration' 
    // with your table name)
    $stmt = $conn->prepare("INSERT INTO users_registration (username, email, password) VALUES (:username, :email, :password)");
    $stmt->bindParam(':username', $username);
    $stmt->bindParam(':email', $email);
    $stmt->bindParam(':password', $password);

    if ($stmt->execute()) {
        http_response_code(201);
        echo json_encode(array("message" => "Registration successful"));
    } else {
        http_response_code(500);
        echo json_encode(array("error" => "Registration failed"));
    }
} catch (PDOException $e) {
    http_response_code(500);
    echo json_encode(array("error" => "Database error: " . $e->getMessage()));
}
?>