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MariaDB

Troubleshooting​

MySQLi "No such file or directory" with Docker Database​

Situation​
  • MariaDB/MySQL running in Docker container
  • Port 3306 exposed to host (0.0.0.0:3306->3306/tcp)
  • PHP application using mysqli driver (e.g., via Dibi/Doctrine)
  • Database connection configured with host: 'localhost'
Symptom​
Fatal error: Uncaught Dibi\DriverException: No such file or directory
in .../MySqliDriver.php:102

The error occurs during database connection, even though:

  • The PHP file exists
  • mysqli extension is installed
  • Docker container is running
  • Port 3306 is accessible
Root Cause​

When PHP's mysqli sees host: 'localhost', it attempts a Unix socket connection and looks for a socket file (e.g., /var/run/mysqld/mysqld.sock). Since the database runs in Docker, no socket file exists on the host filesystem—only the TCP port is exposed.

Solution​

Change database host from localhost to 127.0.0.1 to force TCP connection:

const CONFIG = [
    'database' => [
        'driver' => 'mysqli',
        'host' => '127.0.0.1',  // ← Use IP, not 'localhost'
        'username' => 'root',
        'password' => 'root',
        'database' => 'testdb',
    ],
];
Why This Works​
  • localhost → mysqli uses Unix socket
  • 127.0.0.1 → mysqli uses TCP/IP connection

Docker only exposes TCP ports, not Unix sockets.

Additional Notes​
  • This applies to any PHP mysqli connection to containerized databases
  • Also relevant for PDO MySQL connections with default settings
  • Alternative: Use 127.0.0.1 or actual container IP in all database configs