connect-db.php

<?php
// Remember to start the database server (or GCP SQL instance) before trying to connect to it

////////////////////////////////////////////
/** S22, PHP (on Google Standard App Engine) connect to MySQL instance (GCP) **/
// $username = 'root';                      // or your username
// $password = 'your-root-password';        // or your password
// $host = 'cs4750:us-east4:db-demo';       // projectID = cs4750, SQL instance ID = db-demo
// $dbname = 'guestbook';                   // database name = guestbook
// $dsn = "mysql:unix_socket=/cloudsql/cs4750:us-east4:db-demo;dbname=guestbook";

// to get instance connection name, go to GCP SQL overview page
////////////////////////////////////////////

/** S22, PHP (on local XAMPP or CS server) connect to MySQL instance (GCP) **/
// $username = 'root';                      // or your username
// $password = 'your-root-password';        // or your password
// $host = 'cs4750:us-east4:db-demo';       // projectID = cs4750, SQL instance ID = db-demo
// $dbname = 'guestbook';                   // database name = guestbook
// $dsn = "mysql:host=your-SQL-public-IP-address;dbname=$dbname";       // connect PHP (XAMPP) to DB (GCP)

// to get public IP addres of the SQL instance, go to GCP SQL overview page

// To connect from a local PHP to GCP SQL instance, need to add authorized network
// to allow your machine to connect to the SQL instance. 
// 1. Get IP of the computer that will connect to the SQL instance
//    (use http://ipv4.whatismyv6.com/ to find the IP address)
// 2. On the cloud SQL connections page, add authorized networks, enter the IP address
////////////////////////////////////////////

 
/** S22, PHP (on GCP, local XAMPP, or CS server) connect to MySQL (on CS server) **/
$username = 'drb6pje'; 
$password = 'Winter2022!!';
$host = 'mysql01.cs.virginia.edu';
$dbname = 'drb6pje';
$dsn = "mysql:host=$host;dbname=$dbname";     

////////////////////////////////////////////

// DSN (Data Source Name) specifies the host computer for the MySQL datbase 
// and the name of the database. If the MySQL datbase is running on the same server
// as PHP, use the localhost keyword to specify the host computer

// To connect to a MySQL database, need three arguments: 
// - specify a DSN, username, and password

// Create an instance of PDO (PHP Data Objects) which connects to a MySQL database
// (PDO defines an interface for accessing databases)
// Syntax: 
//    new PDO(dsn, username, password);


/** connect to the database **/
try 
{
   $db = new PDO($dsn, $username, $password);
   $db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
   
   // dispaly a message to let us know that we are connected to the database 
   // echo "<p>You are connected to the database --- dsn=$dsn, user=$username, pwd=$password </p>";
}
catch (PDOException $e)     // handle a PDO exception (errors thrown by the PDO library)
{
   // Call a method from any object, use the object's name followed by -> and then method's name
   // All exception objects provide a getMessage() method that returns the error message 
   $error_message = $e->getMessage();        
   echo "<p>An error occurred while connecting to the database: $error_message </p>";
}
catch (Exception $e)       // handle any type of exception
{
   $error_message = $e->getMessage();
   echo "<p>Error message: $error_message </p>";
}

?>