How to connect multiple MySQL databases on a single webpage ?

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 program to connect multiple MySQL datbase 
// 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>"; 
} 
  
?> 

Output:

My Personal Notes

Oct	NOV	Dec
	12
2018	2019	2020

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