Start on project with the connection services and first command to list databases

src/Console/ListDatabasesCommand.php

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+<?php
+
+namespace App\Console;
+
+use App\Service\DatabaseManager;
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Output\OutputInterface;
+
+class ListDatabasesCommand extends Command
+{
+    // the name of the command (the part after "bin/console")
+    protected static $defaultName = 'app:db:list';
+
+    public function __construct(
+        private DatabaseManager $db,
+    )
+    {
+        parent::__construct();
+    }
+
+    protected function configure(): void
+    {
+        // ...
+    }
+
+    protected function execute(InputInterface $input, OutputInterface $output): int
+    {
+        $dbs = $this->db->listDatabases();
+
+        $output->writeln('List of databases:');
+        foreach ($dbs as $db) {
+            $output->writeln(sprintf(' -%s', $db));
+        }
+
+        return Command::SUCCESS;
+    }
+}

src/Service/DatabaseManager.php

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+<?php
+
+namespace App\Service;
+
+use mysqli;
+
+class DatabaseManager
+{
+    private mysqli $conn;
+
+    public function __construct(
+        private MysqliConnection $service
+    )
+    {
+        $this->conn = $this->service->getConnection();
+    }
+
+    public function listDatabases(): array
+    {
+        $dbs = [];
+        $results = $this->conn->query('SHOW DATABASES');
+        while ($result = $results->fetch_object()) {
+            $dbs[] = $result->Database;
+        }
+
+        return $dbs;
+    }
+}

src/Service/MysqliConnection.php

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+<?php
+
+namespace App\Service;
+
+use mysqli;
+
+class MysqliConnection
+{
+    private mysqli $connection;
+
+    public function __construct($hostname, $user, $password)
+    {
+        $this->connection = new mysqli($hostname, $user, $password);
+        if ($this->connection->connect_error) {
+            throw new \Exception("Connection failed: " . $this->connection->connect_error);
+        }
+    }
+
+    public function getConnection(): mysqli
+    {
+        return $this->connection;
+    }
+}