Common ways to connect to MySQL databases are using mysqli extensions and PDO. 1. Use mysqli to extend the recommended object-oriented method, with clear code, and you need to ensure that extension=mysqli is enabled in php.ini; 2. Use PDO is suitable for compatibility with multiple databases, supports exception handling and set character set to utf8mb4. Frequently asked questions include username and password errors, database does not exist, host or port errors, PHP extensions not enabled, and firewall restrict access. These issues should be checked one by one to ensure successful connection.
Connecting to MySQL database is one of the most basic and common operations when using PHP for back-end development. Although the method is not complicated, many newbies are prone to errors during configuration and use. Let me briefly talk about several common methods and points that need to be paid attention to.
Extend connections using mysqli (recommended)
mysqli is currently the mainstream object-oriented or procedural database connection method, supporting functions such as preprocessing statements and multi-queries.
Basic writing method:
$host = 'localhost';
$user = 'root';
$password = '';
$database = 'test_db';
$conn = new mysqli($host, $user, $password, $database);
if ($conn->connect_error) {
die("Connection failed: " . $conn->connect_error);
}- Make sure the mysqli extension is enabled and you can check whether
extension=mysqliis enabled in php.ini. - If you are using a remote database, remember to modify
$hostto the corresponding address. - It is recommended to use an object-oriented approach, so the code structure is clearer.
Use PDO connection (suitable for situations where multiple databases need to be compatible)
PDO supports multiple database types. If you may migrate to other database systems in the future, such as PostgreSQL, it is more convenient to use PDO.
Sample code:
$host = 'localhost';
$db = 'test_db';
$user = 'root';
$pass = '';
$charset = 'utf8mb4';
$dsn = "mysql:host=$host;dbname=$db;charset=$charset";
$options = [
PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC
];
try {
$pdo = new PDO($dsn, $user, $pass, $options);
} catch (\PDOException $e) {
throw new \PDOException($e->getMessage(), (int)$e->getCode());
}- Error mode and default return format can be controlled by setting options.
- Added exception handling suggestions, so that the problem can be located faster.
- Note that the character set is set to
utf8mb4, otherwise Chinese garbled may appear.
Frequently Asked Questions and Precautions
Not connecting to the database is one of the most common problems for beginners. Here are some troubleshooting directions:
Incorrect username or password
Check for error spelling, or whether the database user permissions are correct.The database does not exist or is not created
To confirm whether the target database exists, you can first view it through phpMyAdmin or the command line.The host name or port is incorrect
The default is localhost and 3306. If the database is deployed elsewhere, it needs to be changed to the host IP or domain name, and sometimes the port must be specified.PHP extension is not enabled
If you are using XAMPP or WAMP, make sure mysqli or pdo_mysql is loaded.Firewall restrict access
If you are connected to a remote database, confirm that the server firewall allows your IP to access port 3306.
Basically that's all. Connecting to the database itself is not difficult, but it takes some time to configure the environment and troubleshoot problems. As long as you get the parameters and extensions right, you can usually connect smoothly.
The above is the detailed content of how to connect to mysql database from php. For more information, please follow other related articles on the PHP Chinese website!
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