Database Abstraction

For our shopping cart we will use a simple database abstraction library. Although this tutorial only use
MySQL but using an abstraction layer is still a good thing. We do this just in sow we can easily migrate to another database.
In case you don’t know, a database abstraction is simply making our own interfaces ( functions ) to call the database function provided by PHP. This way if we change to another database or if the PHP function itself change we just need to modify one file ( database.php ) instead of modifying all our source code.
The database functions is stored in library/database.php. You can see the content below

<?php
require_once ‘config.php’;

$dbConn = mysql_connect ($dbHost, $dbUser, $dbPass) or die (‘MySQL connect failed. ‘ . mysql_error());
mysql_select_db($dbName) or die(‘Cannot select database. ‘ . mysql_error());

function dbQuery($sql)
{
   return mysql_query($sql) or die(‘Query failed. ‘ . mysql_error());
}

function dbAffectedRows()
{
   global $dbConn;

   return mysql_affected_rows($dbConn);
}

function dbFetchArray($result, $resultType = MYSQL_NUM) 
{
   return mysql_fetch_array($result, $resultType);
}

function dbFetchAssoc($result)
{
   return mysql_fetch_assoc($result);
}

function dbFetchRow($result) 
{
   return mysql_fetch_row($result);
}

function dbFreeResult($result)
{
   return mysql_free_result($result);
}

function dbNumRows($result)
{
   return mysql_num_rows($result);
}

function dbSelect($dbName)
{
   return mysql_select_db($dbName);
}
?>

How to use it ?

Below you can see an example on how to use this database abstration library. The first one is using PHP database function directly :
<?php
require_once ‘config.php’;
$conn = mysql_connect($dbHost, $dbUser, $dbPass);
mysql_select_db($dbName);
$sql = “SELECT *
FROM tbl_product
ORDER BY pd_name”;
$result = mysql_query($sql);
$products = array();
while ($row = mysql_fetch_assoc($result)) {
$products[] = $row;
}
?>
And the second one is using our database abstraction. We don’t have to initiate the connection this time because it is done from database.php :

<?php
require_once ‘config.php’;
require_once ‘database.php’;$sql = “SELECT * 
FROM tbl_product
ORDER BY pd_name”;

$result = dbQuery($sql);
$products = array();
while ($row = dbFetchAssoc(&$result)) {
$products[] = $row;
} 
?>
As you can see, using database abstraction isn’t so hard at all.
Now that we have taken care the database issues we start building the admin pages.