Connect to Multiple Databases using MySQLi - php

Question

I need to connect to two databases using PHP and use the results from the first query to get the rest of the data I need out of a second database.
So for the second connection, I need to connect to the second database and Select state and zipcode where the results from connection 1 (client) is equal to the firstname in database 2. How would I do this?
<?php
// check if the 'id' variable is set in URL, and check that it is valid
if (isset($_GET['cd']) && is_numeric($_GET['cd'])) {
// get id value
$id = intval($_GET['cd']);
}
$results = $id;
//Open a new connection to the MySQL server
require "calendarconnect.php";
//chained PHP functions
$client = $mysqli->query("SELECT client FROM appointments WHERE ID = $results")->fetch_object()->client;
print $client; //output value
$mysqli->close();
Connection To Database Code is similar to the below
<?php
//Open a new connection to the MySQL server
$mysqli = new mysqli('localhost','some database','some password','some username');
//Output any connection error
if ($mysqli->connect_error) {
die('Error : ('. $mysqli->connect_errno .') '. $mysqli->connect_error);
}

Answer 1

This isn't tested, but I think it would go something like this.
<?php
$dbc1 = new MySQLi()or die('error connecting to database');
$dbc2 = new MySQLi()or die('error connecting to database');
//build query 1
$query1 = "SELECT * FROM Table";
$result1 = $dbc1->query($query) or die("Error in query");
$thing1 = '';
// check result
if($result1->num_rows){
//fetch result as object
$row = $result1->fetch_object();
//set attributes
$thing1 = $row->Name;
}
//build query 2
$query2 = "SELECT * FROM AnotherTable WHERE Id = '$thing1'";
$result2 = $dbc2->query($query) or die("Error in query");
$thing2 = '';
// check result
if($result2->num_rows){
//fetch result as object
$row = $result2->fetch_object();
//set attributes
$thing2 = $row->Name;
}
?>

Answer 2

You would need to make 2 different connections
<?php
$mysqliDB1 = new mysqli('localhost', 'DB1UserId', 'pwd', 'db1');
$mysqliDB2 = new mysqli('localhost', 'DB2UserId', 'pwd', 'db2');
Now when you use the $mysqliDB1->.... you are talking to the DB1 database and when you use the $mysqliDB2->.... you are talking to the DB2 database
So
$client = $mysqliDB1->query("SELECT client FROM appointments WHERE ID = $results")
->fetch_object();
$locn = $mysqliDB2->query("SELECT state,zipcode
FROM location
WHERE ClientID = {$client->FirstName}")
->fetch_object();
echo $locn->state;
echo $locn->zipcode;
I am guessing the table name and so on, but I am not clarevoyant so you will have to fill that in for yourself.

Answer 3

If you want to perform queries in two databases at the same time you need to have two separate mysqli objects. To open the connection you can use the following code:
// Don't forget to enable error reporting!
mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);
$db1 = new mysqli('localhost', 'user', 'pass', 'dbName');
$db1->set_charset('utf8mb4'); // always set the charset
$db2 = new mysqli('localhost', 'user', 'pass', 'dbName2');
$db2->set_charset('utf8mb4'); // always set the charset
Then you can perform your two statements in each database separately.
// get id value
$id = intval($_GET['cd']);
// Get client name from DB1
$stmt = $db1->prepare('SELECT client FROM appointments WHERE ID = ?');
$stmt->bind_param('s', $id);
$stmt->execute();
$client = $stmt->get_result()->fetch_object();
// Get state and zipcode from DB2
$stmt = $db2->prepare('SELECT state,zipcode FROM location WHERE ClientName = ?');
$stmt->bind_param('s', $client->client);
$stmt->execute();
$location = $stmt->get_result()->fetch_object();
echo $location->state;
echo $location->zipcode;