Creating and Opening a Database

PHP provides several functions for DBA. The first function you must know is the dba_open() function. This will allow you to create a database, write to a database, read a database, or truncate a database.

int dba_open(string sPath, string sMode, string sHandler, [int nMod]);

The first parameter of the dba_open() function is the path to the database; the second parameter is the mode in which you wish to open the database. Possible values for this can be any of the following:

• r – Open the database for reading.

• w – Open the database for writing.

• c – Create a new database.

• n – Truncate a database.

The third parameter is the name of the handler for the type of database you would like to use. The third parameter can be any of the following values:

• dbm – Berkley DB-style database (deprecated).

• ndbm – A newer Berkley DB-style database. This is very limited and is also deprecated.

• gdbm – The GNU database.

• db3 – The DB3 database toolkit from Sleepycat Software. This will be the database type that you will use in your projects.

• cdb – Qmail database. This format only supports reading operations.

The optional fourth parameter specifies the mode in which the database should open. This is not a commonly used parameter and you won’t be using it in your games.

The dba_open() function will return a handle for the database if it was successful; otherwise it returns 0 or false when it fails. This will allow you to verify that the database is open. If the open fails you can trap for it and either print a warning message or exit the application altogether. Take a look at the following code example to see how to use the dba_open() function.

<?php
// Set the db parameters
$dbPath = “myDatabase.db”;
$dbType = “db3”;

function CreateDatabase($thePath, $theType)
{
    $db = dba_open($thePath, “c”, $theType);
    if(!$db)
    {
        printf(“Could not create the database”);
        return 0;
    }

    return $db;
}
 
function OpenDatabase($thePath, $theType)
{
    $db = dba_open($thePath, “r”, $theType);
    if(!$db)
    {
        printf(“Could not open the database”);
        return 0;
    }
        
        return $db;
}

// Open the database, if it isn’t there, create it
$db = OpenDatabase($dbPath, $dbType);
if(!$db)
{
    $db = CreateDatabase($dbPath, $dbType);
    if(!$db)
    {
        exit;
    }
}

// If you get here the database has opened successfully and you can do what you want
with it.
?>