Connecting to MySQL

Summary: in this tutorial, you’ll learn step by step how to connect to a MySQL database from PHP using PDO.

Prerequisites

Before connecting to a MySQL database server, you need to have:

  • A MySQL database server, a database, and an account that has access to the database.
  • PDO MySQL driver enabled in the php.ini file

1) Setting MySQL database parameters

Suppose you have a local MySQL database server that has the following information:

  • The host is localhost.
  • The bookdb database on the local database server.
  • The account with the user root and password 'S@cr@t1!' that can access the bookdb database.

In PHP, you can create a config.php file and place the database parameters:

<?php $host = 'localhost'; $db = 'bookdb'; $user = 'root'; $password = 'S@cr@t1!';
Code language: HTML, XML (xml)

To use the database parameters, you can include the config.php file using the require construct:

<?php require 'config.php';
Code language: HTML, XML (xml)

2) Enable PDO_MySQL Driver

PDO_MYSQL is a driver that implements the PDO interface. PDO uses the PDO_MYSQL driver to connect to a MySQL database.

To check if the PDO_MYSQL driver is enabled, you open the php.ini file. The php.ini file is often located under the php directory. For example, you can find the php.ini file under the C:\xampp\php directory if you use XAMPP on Windows.

The following shows the extension line in the php.ini file:

;extension=php_pdo_mysql.dll

To enable the extension, you need to uncomment it by removing the semicolon (;) from the beginning of the line like this:

extension=php_pdo_mysql.dll

After that, you need to restart the web server for the change to take effect.

MySQL data source name

PDO uses a data source name (DSN) that contains the following information:

  • The database server host
  • The database name
  • The user
  • The password
  • and other parameters such as character sets, etc.

PDO uses this information to make a connection to the database server. To connect to the MySQL database server, you use the following data source name format:

"mysql:host=host_name;dbname=db_name;charset=UTF8"
Code language: JSON / JSON with Comments (json)

For example:

$dsn = "mysql:host=localhost;dbname=bookdb;charset=UTF8";
Code language: PHP (php)

Note that the charset UTF-8 sets the character set of the database connection to UTF-8.

Connecting to MySQL

The following index.php script illustrates how to connect to the bookdb database on the MySQL database server with the root account:

<?php require 'config.php'; $dsn = "mysql:host=$host;dbname=$db;charset=UTF8"; try { $pdo = new PDO($dsn, $user, $password); if ($pdo) { echo "Connected to the $db database successfully!"; } } catch (PDOException $e) { echo $e->getMessage(); }
Code language: HTML, XML (xml)

How it works.

  • First, create a new PDO object with the data source name, user, and password. The PDO object is an instance of the PDO class.
  • Second, show the success message if the connection is established successfully or an error message if an error occurs.

If you have everything set up correctly, you will see the following message:

Connected to the bookdb database successfully!
Code language: plaintext (plaintext)

Error handling strategies

PDO supports three different error handling strategies:

  • PDO::ERROR_SILENT – PDO sets an error code for inspecting using the PDO::errorCode() and PDO::errorInfo() methods. The PDO::ERROR_SILENT is the default mode.
  • PDO::ERRMODE_WARNING – Besides setting the error code, PDO will issue an E_WARNING message.
  • PDO::ERRMODE_EXCEPTION – Besides setting the error code, PDO will raise a PDOException.

To set the error handling strategy, you can pass an associative array to the PDO constructor like this:

$pdo = new PDO($dsn, $user, $password, [PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION]);
Code language: PHP (php)

Or you can use the setAttribute() method of the PDO instance:

$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
Code language: PHP (php)

Troubleshooting

There are some common issues when you connect to a MySQL database:

If the MySQL driver is not enabled in the php.ini file, you will get the error message:

could not find driver
Code language: plaintext (plaintext)

If you provide an incorrect password, you get the following error message:

SQLSTATE[HY000] [1045] Access denied for user 'root'@'localhost' (using password: YES)
Code language: plaintext (plaintext)

If you provide an invalid database name or the database does not exist, you get the following error message:

SQLSTATE[HY000] [1049] Unknown database 'bookdb'
Code language: plaintext (plaintext)

If you provide an invalid database hostname, the following error message will display:

SQLSTATE[HY000] [2002] php_network_getaddresses: getaddrinfo failed: No such host is known.
Code language: plaintext (plaintext)

Summary

  • Enable the PDO_MYSQL driver in the php.ini file for connecting to a MySQL database from PHP PDO.
  • Create an instance of the PDO class to make a connection to a MySQL database.
  • Use the PDO constructor or the setAttribute() method to set an error handling strategy.
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