Mysql - Couldn't connect unknown database 'databasename' error

问题

I am using PDO to connect to mySql database. I am not able to connect to any database that I create although I can connect to already created databases( already created by default). I am using wamp server.

<?php
try{
$dbh=new PDO("mysql:host=localhost;dbname=mydata","root","");
}catch(Exception $e){
    die("ERROR: Couldn't connect. {$e->getMessage()}");
}
?>

If i substitute mydata with mysql which is previously created database in wamp server, then the code works perfectly. The only problem is with the databases that I create. I have tried giving mydata the same privileges as mysql database but it doesn't work.

回答1:

you have multiple database servers on your PC running and your code and your phpmyadmin connect to different databases

To get a proof, run the following query in phpmyadmin:

show databases;

And then run the same query in PDO:

$host = 'your db host';
$user = 'your db username';
$pass = 'your db password';

$pdo = new PDO("mysql:host=localhost", $user, $pass, [PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION]);
$databases = $pdo->query('show databases')->fetchAll(PDO::FETCH_COLUMN);
var_dump($databases);

and compare the output. It will show you that either there is a spelling error or indeed phpmyadmin and PHP are connected to different database servers.