Question

I am used to mysql database access using the procedural mysql method. I am a beginner – intermediate programmer.

I am trying to learn the PDO api, however all resources which discuss using PDO show the connection string, username and password.

e.g.

<?php

try {
    $db_conn = new PDO('mysql:host=localhost;dbname=databaseName','username', 'password');  
} 
catch (PDOException $e) {
    echo 'Could not connect to database';
}


$sql = 'SELECT * FROM Products';
$stmt = $db_conn->prepare($sql);

...
...
...

?>

What I want, and think would be better programming is to put my PDO connection into a new file. then where I want to run an SQL query, I require_once(‘PDO.php’) or similar.

The problem I have with this is as follows:

1. How do I close the connection? Simply $db_conn = null; ??
2. Should I close the connection after each query is run, then re-open the connection?
3. Should I close the connection or is it automatically destroyed when the user closes the browser?

I am working from a book called PHP Master: Writing Cutting Edge Code. http://www.sitepoint.com/books/phppro1/ and this has completely omitted any reference to closing the connection / destroying the object after it has been used.

Furthermore, I have looked at online tutorials, and they all connect to the database using PDO inline as opposed to having a separate database connector. This I am not happy with for many reasons:

1. I have to type username & password to connect every time.
2. If I get a developer to take a look at code / write some code, they will all have access to the database.
3. If I change the DB username & Password, then each file which connects to the database will need to be updated.

Could anybody recommend a better resource? Could anybody advise on what is the best practice way to do this?

Many thanks

Answer 1

Your question about how to store the database name, username and password have nothing to do with the capabilities of PDO. This is an implementation choice. The way you use to work with procedural functions can also be applied to PDO, the difference is that with PDO you work with objects instead.

So for simplicity, store the PDO creation of an object, either in a function or class, in which you can create the PDO instance anytime, e.g.

function createPDO($cfg) {
  try {
    return new PDO("mysql:host=".$cfg['host'].",port:".($cfg['port']).";dbname=".($cfg['name']).";",$cfg['username'], $cfg['password']);
  } catch(PDOException $e) {
    // handle exceptions accordingly
  }
}

You can centralise these in whatever PHP file you like to include, just like you were used with the procedural functions.

You have two choices, either put all the relevant database information inside the createPDO, or use something like a config ($cfg) variable to store all this information.

$config = array();
$config['db'] = array(
  'host' => 'localhost',
  'name' => 'databse',
  'username' => 'userx',
  'password' => 'passy'
  /* .. etc */
)

Using the createPDO function would be as followed

$db_conn = createPDO($config['db']);

For connections closing, each connection made to the database automatically disconnects after PHP exits its execution. You can however, close the connection if you wish, by setting the variable of the PDO object you assigned it to, in this example (and in yours) $db_conn to null

$db_conn = null; // connection closed.

The PDO has a manual http://php.net/manual/en/book.pdo.php here, which is a good start getting to know PDO a bit better.