<?php
$pdo = new PDO('mysql:host=localhost;dbname=databaseA', 'root', 'mysql'); //Database 1
$pdo2 = new PDO('mysql:host=localhost;dbname=databaseB', 'root', 'mysql'); //Database 2
$sql = "SELECT a.userID, b.usersFirstName, b.usersLastName FROM databaseA.dbo.TableA a inner join database B.dbo.TableB b ON a.userID=b.userID";
foreach ($pdo->query($sql) as $row) {
$jo1 = $row['userID'];
$jo2 = $row['usersFirstName'];
}
?>