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When working with databases, you may have used a graphical tool such as Postbird, PgAdmin, or PhpMyAdmin. These tools are clients, which create a connection to the database server and send commands to it.

Similarly, we will be setting up PHP to act as a client which will send queries to PostgreSQL.

To connect to a server, a client needs to know where it is. We provide this information in the form of a DSN (data source name), which holds our database type (PostgreSQL), hostname, and database name. The hostname contains the location of the database. If PostgreSQL is running on the same host (computer) as PHP, we use localhost. If it’s running on a remote server, we use its IP address or domain name. For Codecademy’s environment, we will use /tmp.

// Assign variables for the hostname and database name $hostname = '/tmp'; $dbname = 'ccuser'; // Create the DSN (data source name) $dsn = "pgsql:host=$hostname;dbname=$dbname";

The first part of the DSN is the prefix, where we specify which database system to use. For PostgreSQL, that is pgsql. Then we add a colon, followed by a key/value pair containing the hostname and database name, separated by a semi-colon. The DSN uses a precise format, so it’s important not to include spaces or extra characters.

We’ll also need to store the username and password of an account with the correct permissions for the database.

$username = 'ccuser'; $password = 'pass';

We’ll start the connection by creating a database object from the PDO class and instantiating it using the new keyword. The PDO constructor takes the $dsn, $username, and $password variables as its arguments in that order. If the connection is successful, the database object will be assigned to $db.

$db = new PDO($dsn, $username, $password);

After we complete our database operations, we will end the connection by setting the database object and any of its references to null. We can do this with:

$db = null;

Instructions

1.

Let’s start by declaring variables we need to connect to our PostgreSQL database. Set $hostname as '/tmp', $dbname as 'ccuser', $username as 'ccuser', and $password as 'pass'.

Make sure you declare the variables at the top of the code.

2.

Using the variables we just declared, create a $dsn variable and set it to a DSN for our PostgreSQL database.

3.

Next, create a database object to start the connection using a PDO object. Store the database object in a variable named $db.

4.

At the end of the code, after all database operations are complete, terminate the connection by setting the database object to null.

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