How to connect multiple MySQL databases on a single webpage ?

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This article explains how to connect multiple MySQL databases into a single webpage. It is useful to access data from multiple databases.

There are two methods to connect multiple MySQL databases into a single webpage which are:

Using MySQLi (Improved version of MySQL)
Using PDO (PHP Data Objects)

Syntax:

MySQLi Procedural syntax:

$link = mysqli_connect( “host_name”, “user_name”, “password”, “database_name” );

MySQLi Object Oriented syntax:

$link = new mysqli( “host_name”, “user_name”, “password”, “database_name” );

PDO (PHP Data Objects) syntax:

$pdo = new PDO( “mysql:host=host_name; dbname=database_name”, “user_name”, “password” );

Program: This program uses MySQLi to connect multiple databases on a single webpage.

PHP

<?php
// PHP program to connect multiple MySQL database
// into single webpage
 
// Connection of first database
// Database name => database1
// Default username of localhost => root
// Default password of localhost is '' (none)
$link1 = mysqli_connect("localhost", "root", "", "database1");
 
// Check for connection
if($link1 == true) {
    echo "database1 Connected Successfully";
}
else {
    die("ERROR: Could not connect " . mysqli_connect_error());
}
 
echo "<br>";
 
// Connection of first database
// Database name => database1
$link2 = mysqli_connect("localhost", "root", "", "database2");
 
// Check for connection
if($link2 == true) {
    echo "database2 Connected Successfully";
}
else {
    die("ERROR: Could not connect " . mysqli_connect_error());
}
 
echo "<br><br>Display the list of all Databases:<br>";
 
// Connection of databases
$link = mysqli_connect('localhost', 'root', '');
 
// Display the list of all database name
$res = mysqli_query($link, "SHOW DATABASES");
 
while( $row = mysqli_fetch_assoc($res) ) {
    echo $row['Database'] . "<br>";
}
 
?>