Connection using PDO [closed]

Answer 1

The problem is caused by 2 syntax errors in your Data Source Name (DSN) (the first argument in the PDO connection string).

The errors

1. You cannot pass your db constant into the connection string as "...dbname = db". Since db is wrapped in double quotes and will be interpretted as a string instead of a constant.

2. You cannot have spaces in your DSN. It should be:

   "mysql:host=localhost;dbname=login_db" //no spaces.
   

I've tested this and it exhibits some strange behaviour:

• Specifically, it seems that the space between host and the first = sign causes the problem. If there is a space, it will echo "You are connected" even if "localhost" is misspelled.
• Similarly, if there is a space between dbname and its = sign, it will appear to connect even if the specified database name is incorrect.

My guess is that this is some quirk of how the PDO class parses the DSN.

The solution

Remove all the spaces from the DSN.

You also need to pass in your database name in a different way. There are different ways to fix this. I would recommend, for the sake of not getting any more weird-to-debug-errors, that you use variables instead of constant definitions:

$host = 'localhost';
$user = 'root';
$pass = '';
$db   = 'login_db';

try{
    $dbh = new PDO("mysql:host=$host;dbname=$db",$user,$pass);
    echo "You are connected";
}
catch(PDOException $e){
    echo $e -> getMessage(); 
}

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As for good tutorials, you can look at these:

Net.tuts+ : PHP Database Access

Net.tuts+ : Why use PDOs

And of course the don't forget the php.net docs.

php.net : PDOs

Answer 2

Constant identifiers should be uppercase:

 define('USER','root');

If you want to use constants you can do it this way:

$dbh = new PDO("mysql:host = ". HOST .";dbname=" . DB ,USER,PASS);