diff --git a/phpBB/config/default/container/services_db.yml b/phpBB/config/default/container/services_db.yml
index bad99b7d87..4ead52126c 100644
--- a/phpBB/config/default/container/services_db.yml
+++ b/phpBB/config/default/container/services_db.yml
@@ -8,7 +8,9 @@ services:
         synthetic: true
 
     dbal.conn.doctrine:
-        synthetic: true
+        class: Doctrine\DBAL\Connection
+        factory: ['phpbb\db\doctrine\connection_factory', 'get_connection']
+        arguments: ['@config.php']
 
 # ----- DB Tools -----
     dbal.tools.factory:
diff --git a/phpBB/phpbb/db/doctrine/comparator.php b/phpBB/phpbb/db/doctrine/comparator.php
index 27390e3da0..4a3d3c14f6 100644
--- a/phpBB/phpbb/db/doctrine/comparator.php
+++ b/phpBB/phpbb/db/doctrine/comparator.php
@@ -4,7 +4,7 @@
  * This file is part of the phpBB Forum Software package.
  *
  * @copyright (c) phpBB Limited <https://www.phpbb.com>
- * @license       GNU General Public License, version 2 (GPL-2.0)
+ * @license GNU General Public License, version 2 (GPL-2.0)
  *
  * For full copyright and license information, please see
  * the docs/CREDITS.txt file.
@@ -50,7 +50,7 @@ class comparator extends \Doctrine\DBAL\Schema\Comparator
 				}
 
 				$index_columns = array_map('strtolower', $index->getUnquotedColumns());
-				if (array_search($columnName, $index_columns, true) === false)
+				if (!in_array($columnName, $index_columns, true))
 				{
 					continue;
 				}
diff --git a/phpBB/phpbb/db/doctrine/connection_factory.php b/phpBB/phpbb/db/doctrine/connection_factory.php
index 4d2c2f55e6..b692309688 100644
--- a/phpBB/phpbb/db/doctrine/connection_factory.php
+++ b/phpBB/phpbb/db/doctrine/connection_factory.php
@@ -4,7 +4,7 @@
  * This file is part of the phpBB Forum Software package.
  *
  * @copyright (c) phpBB Limited <https://www.phpbb.com>
- * @license       GNU General Public License, version 2 (GPL-2.0)
+ * @license GNU General Public License, version 2 (GPL-2.0)
  *
  * For full copyright and license information, please see
  * the docs/CREDITS.txt file.
diff --git a/phpBB/phpbb/db/doctrine/oci8/connection.php b/phpBB/phpbb/db/doctrine/oci8/connection.php
index 98d11c2fbe..6f7f0aa3b9 100644
--- a/phpBB/phpbb/db/doctrine/oci8/connection.php
+++ b/phpBB/phpbb/db/doctrine/oci8/connection.php
@@ -4,7 +4,7 @@
  * This file is part of the phpBB Forum Software package.
  *
  * @copyright (c) phpBB Limited <https://www.phpbb.com>
- * @license       GNU General Public License, version 2 (GPL-2.0)
+ * @license GNU General Public License, version 2 (GPL-2.0)
  *
  * For full copyright and license information, please see
  * the docs/CREDITS.txt file.
@@ -18,7 +18,7 @@ use Doctrine\DBAL\Driver\Result as DriverResult;
 use Doctrine\DBAL\Driver\Statement as DriverStatement;
 use Doctrine\DBAL\ParameterType;
 
-class Connection implements DriverConnection
+class connection implements DriverConnection
 {
 	/**
 	 * @var DriverConnection
@@ -68,7 +68,7 @@ class Connection implements DriverConnection
 	/**
 	 * {@inheritDoc}
 	 */
-	public function lastInsertId($name = null)
+	public function lastInsertId($name = null): ?string
 	{
 		return $this->wrapped->lastInsertId($name);
 	}
@@ -76,7 +76,7 @@ class Connection implements DriverConnection
 	/**
 	 * {@inheritDoc}
 	 */
-	public function beginTransaction()
+	public function beginTransaction(): bool
 	{
 		return $this->wrapped->beginTransaction();
 	}
@@ -84,7 +84,7 @@ class Connection implements DriverConnection
 	/**
 	 * {@inheritDoc}
 	 */
-	public function commit()
+	public function commit(): bool
 	{
 		return $this->wrapped->commit();
 	}
@@ -92,7 +92,7 @@ class Connection implements DriverConnection
 	/**
 	 * {@inheritDoc}
 	 */
-	public function rollBack()
+	public function rollBack(): bool
 	{
 		return $this->wrapped->rollBack();
 	}
diff --git a/phpBB/phpbb/db/doctrine/oci8/driver.php b/phpBB/phpbb/db/doctrine/oci8/driver.php
index 0a5300092c..9a2c67aee0 100644
--- a/phpBB/phpbb/db/doctrine/oci8/driver.php
+++ b/phpBB/phpbb/db/doctrine/oci8/driver.php
@@ -4,7 +4,7 @@
  * This file is part of the phpBB Forum Software package.
  *
  * @copyright (c) phpBB Limited <https://www.phpbb.com>
- * @license       GNU General Public License, version 2 (GPL-2.0)
+ * @license GNU General Public License, version 2 (GPL-2.0)
  *
  * For full copyright and license information, please see
  * the docs/CREDITS.txt file.
diff --git a/phpBB/phpbb/db/doctrine/oci8/result.php b/phpBB/phpbb/db/doctrine/oci8/result.php
index 60072bfe9f..1ab1085427 100644
--- a/phpBB/phpbb/db/doctrine/oci8/result.php
+++ b/phpBB/phpbb/db/doctrine/oci8/result.php
@@ -4,7 +4,7 @@
  * This file is part of the phpBB Forum Software package.
  *
  * @copyright (c) phpBB Limited <https://www.phpbb.com>
- * @license       GNU General Public License, version 2 (GPL-2.0)
+ * @license GNU General Public License, version 2 (GPL-2.0)
  *
  * For full copyright and license information, please see
  * the docs/CREDITS.txt file.
diff --git a/phpBB/phpbb/db/doctrine/oci8/schema_manager.php b/phpBB/phpbb/db/doctrine/oci8/schema_manager.php
index aeb1120e12..c0b2caea1d 100644
--- a/phpBB/phpbb/db/doctrine/oci8/schema_manager.php
+++ b/phpBB/phpbb/db/doctrine/oci8/schema_manager.php
@@ -4,7 +4,7 @@
  * This file is part of the phpBB Forum Software package.
  *
  * @copyright (c) phpBB Limited <https://www.phpbb.com>
- * @license       GNU General Public License, version 2 (GPL-2.0)
+ * @license GNU General Public License, version 2 (GPL-2.0)
  *
  * For full copyright and license information, please see
  * the docs/CREDITS.txt file.
diff --git a/phpBB/phpbb/db/doctrine/oci8/statement.php b/phpBB/phpbb/db/doctrine/oci8/statement.php
index 332c3fab32..bca22473c4 100644
--- a/phpBB/phpbb/db/doctrine/oci8/statement.php
+++ b/phpBB/phpbb/db/doctrine/oci8/statement.php
@@ -4,7 +4,7 @@
  * This file is part of the phpBB Forum Software package.
  *
  * @copyright (c) phpBB Limited <https://www.phpbb.com>
- * @license       GNU General Public License, version 2 (GPL-2.0)
+ * @license GNU General Public License, version 2 (GPL-2.0)
  *
  * For full copyright and license information, please see
  * the docs/CREDITS.txt file.
@@ -35,7 +35,7 @@ class statement implements DriverStatement
 	/**
 	 * {@inheritDoc}
 	 */
-	public function bindValue($param, $value, $type = ParameterType::STRING)
+	public function bindValue($param, $value, $type = ParameterType::STRING): bool
 	{
 		return $this->wrapped->bindValue($param, $value, $type);
 	}
@@ -43,7 +43,7 @@ class statement implements DriverStatement
 	/**
 	 * {@inheritDoc}
 	 */
-	public function bindParam($param, &$variable, $type = ParameterType::STRING, $length = null)
+	public function bindParam($param, &$variable, $type = ParameterType::STRING, $length = null): bool
 	{
 		return $this->wrapped->bindParam($param, $variable, $type, $length);
 	}
diff --git a/phpBB/phpbb/db/doctrine/oracle_platform.php b/phpBB/phpbb/db/doctrine/oracle_platform.php
index 43ace17795..7d9e4a7c28 100644
--- a/phpBB/phpbb/db/doctrine/oracle_platform.php
+++ b/phpBB/phpbb/db/doctrine/oracle_platform.php
@@ -47,7 +47,7 @@ class oracle_platform extends OraclePlatform
 	/**
 	 * {@inheritDoc}
 	 */
-	public function getCreateIndexSQL(Index $index, $table)
+	public function getCreateIndexSQL(Index $index, $table): string
 	{
 		if ($table instanceof Table)
 		{
@@ -79,12 +79,12 @@ class oracle_platform extends OraclePlatform
 	/**
 	 * Check whether the index name is too long
 	 *
-	 * @param string $table_name
-	 * @param string $index_name
-	 * @param bool $throw_error
+	 * @param string	$table_name
+	 * @param string	$index_name
+	 * @param bool		$throw_error
 	 * @return string	The index name, shortened if too long
 	 */
-	protected function check_index_name_length($table_name, $index_name, $throw_error = true)
+	protected function check_index_name_length(string $table_name, string $index_name, bool $throw_error = true): string
 	{
 		$max_index_name_length = $this->getMaxIdentifierLength();
 		if (strlen($index_name) > $max_index_name_length)
@@ -108,7 +108,9 @@ class oracle_platform extends OraclePlatform
 
 			if ($throw_error)
 			{
-				trigger_error("Index name '$index_name' on table '$table_name' is too long. The maximum is $max_index_name_length characters.", E_USER_ERROR);
+				throw new \InvalidArgumentException(
+					"Index name '$index_name' on table '$table_name' is too long. The maximum is $max_index_name_length characters."
+				);
 			}
 		}
 
@@ -118,9 +120,9 @@ class oracle_platform extends OraclePlatform
 	/**
 	 * {@inheritdoc}
 	 */
-	public function getIdentitySequenceName($tableName, $columnName)
+	public function getIdentitySequenceName($tableName, $columnName): string
 	{
-		return $tableName.'_SEQ';
+		return $tableName . '_SEQ';
 	}
 
 	/**
@@ -140,7 +142,7 @@ class oracle_platform extends OraclePlatform
 	/**
 	 * @see OraclePlatform::normalizeIdentifier()
 	 */
-	private function doctrine_normalize_identifier($name)
+	private function doctrine_normalize_identifier($name): Identifier
 	{
 		$identifier = new Identifier($name);
 
@@ -150,7 +152,7 @@ class oracle_platform extends OraclePlatform
 	/**
 	 * @see OraclePlatform::getAutoincrementIdentifierName()
 	 */
-	private function get_doctrine_autoincrement_identifier_name(Identifier $table)
+	private function get_doctrine_autoincrement_identifier_name(Identifier $table): string
 	{
 		$identifierName = $this->add_doctrine_Suffix($table->getName(), '_AI_PK');
 
diff --git a/phpBB/phpbb/db/doctrine/postgresql_platform.php b/phpBB/phpbb/db/doctrine/postgresql_platform.php
index 197f9ac386..5ebff66200 100644
--- a/phpBB/phpbb/db/doctrine/postgresql_platform.php
+++ b/phpBB/phpbb/db/doctrine/postgresql_platform.php
@@ -95,7 +95,7 @@ class postgresql_platform extends PostgreSQL94Platform
 		$post_sql = [];
 		foreach ($columns as $column_name => $column)
 		{
-			if (! empty($column['autoincrement']))
+			if (!empty($column['autoincrement']))
 			{
 				$sequence = new Sequence($this->getIdentitySequenceName($name, $column_name));
 				$sql[] = $this->getCreateSequenceSQL($sequence);
@@ -113,7 +113,8 @@ class postgresql_platform extends PostgreSQL94Platform
 	}
 
 	/**
-	 * @param mixed[] $column
+	 * @param array $column
+	 * @return bool
 	 */
 	private function isSerialColumn(array $column): bool
 	{
@@ -138,7 +139,7 @@ class postgresql_platform extends PostgreSQL94Platform
                        1 AS increment_by
                 FROM   information_schema.sequences
                 WHERE  sequence_schema NOT LIKE 'pg\_%'
-                AND    sequence_schema != 'information_schema'";
+                AND    sequence_schema <> 'information_schema'";
 	}
 
 	/**
diff --git a/phpBB/phpbb/db/doctrine/sqlsrv_platform.php b/phpBB/phpbb/db/doctrine/sqlsrv_platform.php
index 58deed2423..aa7c9bc241 100644
--- a/phpBB/phpbb/db/doctrine/sqlsrv_platform.php
+++ b/phpBB/phpbb/db/doctrine/sqlsrv_platform.php
@@ -4,7 +4,7 @@
  * This file is part of the phpBB Forum Software package.
  *
  * @copyright (c) phpBB Limited <https://www.phpbb.com>
- * @license       GNU General Public License, version 2 (GPL-2.0)
+ * @license GNU General Public License, version 2 (GPL-2.0)
  *
  * For full copyright and license information, please see
  * the docs/CREDITS.txt file.
@@ -37,7 +37,7 @@ class sqlsrv_platform extends SQLServer2012Platform
 				$this->generate_doctrine_identifier_name($column['name']),
 			], [
 				$table,
-				$column['name'].'_1',
+				$column['name'] . '_1',
 			],
 			$sql);
 	}
@@ -70,7 +70,7 @@ class sqlsrv_platform extends SQLServer2012Platform
 		$phpbb_names[] = $diff->name;
 
 		// NEW Table name if relevant
-		if ($diff->getNewName() != null)
+		if ($diff->getNewName())
 		{
 			$doctrine_names[] = $this->generate_doctrine_identifier_name($diff->getNewName()->getName());
 			$phpbb_names[] = $diff->getNewName()->getName();
@@ -79,30 +79,30 @@ class sqlsrv_platform extends SQLServer2012Platform
 		foreach ($diff->addedColumns as $column)
 		{
 			$doctrine_names[] = $this->generate_doctrine_identifier_name($column->getQuotedName($this));
-			$phpbb_names[] = $column->getQuotedName($this).'_1';
+			$phpbb_names[] = $column->getQuotedName($this) . '_1';
 		}
 
 		foreach ($diff->removedColumns as $column)
 		{
 			$doctrine_names[] = $this->generate_doctrine_identifier_name($column->getQuotedName($this));
-			$phpbb_names[] = $column->getQuotedName($this).'_1';
+			$phpbb_names[] = $column->getQuotedName($this) . '_1';
 		}
 
 		foreach ($diff->renamedColumns as $column)
 		{
 			$doctrine_names[] = $this->generate_doctrine_identifier_name($column->getQuotedName($this));
-			$phpbb_names[] = $column->getQuotedName($this).'_1';
+			$phpbb_names[] = $column->getQuotedName($this) . '_1';
 		}
 
 		foreach ($diff->changedColumns as $column)
 		{
 			$doctrine_names[] = $this->generate_doctrine_identifier_name($column->column->getQuotedName($this));
-			$phpbb_names[] = $column->column->getQuotedName($this).'_1';
+			$phpbb_names[] = $column->column->getQuotedName($this) . '_1';
 
 			if ($column->oldColumnName != $column->column->getQuotedName($this))
 			{
 				$doctrine_names[] = $this->generate_doctrine_identifier_name($column->oldColumnName);
-				$phpbb_names[] = $column->oldColumnName.'_1';
+				$phpbb_names[] = $column->oldColumnName . '_1';
 			}
 		}
 
@@ -116,7 +116,7 @@ class sqlsrv_platform extends SQLServer2012Platform
 	 *
 	 * @return string
 	 */
-	private function generate_doctrine_identifier_name($identifier)
+	private function generate_doctrine_identifier_name(string $identifier): string
 	{
 		// Always generate name for unquoted identifiers to ensure consistency.
 		$identifier = new Identifier($identifier);
@@ -132,7 +132,7 @@ class sqlsrv_platform extends SQLServer2012Platform
 	 *
 	 * @return string
 	 */
-	private function generate_doctrine_default_constraint_name($table, $column)
+	private function generate_doctrine_default_constraint_name(string $table, string $column): string
 	{
 		return 'DF_' . $this->generate_doctrine_identifier_name($table) . '_' . $this->generate_doctrine_identifier_name($column);
 	}
diff --git a/phpBB/phpbb/db/doctrine/table_helper.php b/phpBB/phpbb/db/doctrine/table_helper.php
index 422c71a240..92f2069715 100644
--- a/phpBB/phpbb/db/doctrine/table_helper.php
+++ b/phpBB/phpbb/db/doctrine/table_helper.php
@@ -4,13 +4,12 @@
  * This file is part of the phpBB Forum Software package.
  *
  * @copyright (c) phpBB Limited <https://www.phpbb.com>
- * @license       GNU General Public License, version 2 (GPL-2.0)
+ * @license GNU General Public License, version 2 (GPL-2.0)
  *
  * For full copyright and license information, please see
  * the docs/CREDITS.txt file.
  *
  */
-
 namespace phpbb\db\doctrine;
 
 use InvalidArgumentException;
diff --git a/phpBB/phpbb/db/tools/doctrine.php b/phpBB/phpbb/db/tools/doctrine.php
index 631e4dc811..14c5aede2a 100644
--- a/phpBB/phpbb/db/tools/doctrine.php
+++ b/phpBB/phpbb/db/tools/doctrine.php
@@ -4,7 +4,7 @@
  * This file is part of the phpBB Forum Software package.
  *
  * @copyright (c) phpBB Limited <https://www.phpbb.com>
- * @license       GNU General Public License, version 2 (GPL-2.0)
+ * @license GNU General Public License, version 2 (GPL-2.0)
  *
  * For full copyright and license information, please see
  * the docs/CREDITS.txt file.
@@ -32,7 +32,7 @@ use phpbb\db\doctrine\table_helper;
  * In general, it is recommended to use Doctrine directly instead of this class as this
  * implementation is only a BC layer.
  */
-class doctrine implements tools_interface, tools
+class doctrine implements tools_interface
 {
 	/**
 	 * @var AbstractSchemaManager
@@ -181,49 +181,49 @@ class doctrine implements tools_interface, tools
 			return;
 		}
 
-		return $this->_alter_schema(
+		return $this->alter_schema(
 			function (Schema $schema) use($schema_changes): void
 			{
 				$mapping = [
 					'drop_tables' => [
-						'method' => '_schema_drop_table',
+						'method' => 'schema_drop_table',
 						'use_key' => false,
 					],
 					'add_tables' => [
-						'method' => '_schema_create_table',
+						'method' => 'schema_create_table',
 						'use_key' => true,
 					],
 					'change_columns' => [
-						'method' => '_schema_column_change_add',
+						'method' => 'schema_column_change_add',
 						'use_key' => true,
 						'per_table' => true,
 					],
 					'add_columns' => [
-						'method' => '_schema_column_add',
+						'method' => 'schema_column_add',
 						'use_key' => true,
 						'per_table' => true,
 					],
 					'drop_columns' => [
-						'method' => '_schema_column_remove',
+						'method' => 'schema_column_remove',
 						'use_key' => false,
 						'per_table' => true,
 					],
 					'drop_keys' => [
-						'method' => '_schema_index_drop',
+						'method' => 'schema_index_drop',
 						'use_key' => false,
 						'per_table' => true,
 					],
 					'add_primary_keys' => [
-						'method' => '_schema_create_primary_key',
+						'method' => 'schema_create_primary_key',
 						'use_key' => true,
 					],
 					'add_unique_index' => [
-						'method' => '_schema_create_unique_index',
+						'method' => 'schema_create_unique_index',
 						'use_key' => true,
 						'per_table' => true,
 					],
 					'add_index' => [
-						'method' => '_schema_create_index',
+						'method' => 'schema_create_index',
 						'use_key' => true,
 						'per_table' => true,
 					],
@@ -233,12 +233,10 @@ class doctrine implements tools_interface, tools
 				{
 					if (array_key_exists($action, $schema_changes))
 					{
-						foreach ($schema_changes[$action] as $key => $data)
+						foreach ($schema_changes[$action] as $table_name => $table_data)
 						{
 							if (array_key_exists('per_table', $params) && $params['per_table'])
 							{
-								$table_name = $key;
-								$table_data = $data;
 								foreach ($table_data as $key => $data)
 								{
 									if ($params['use_key'] == false)
@@ -255,11 +253,11 @@ class doctrine implements tools_interface, tools
 							{
 								if ($params['use_key'] == false)
 								{
-									$this->{$params['method']}($schema, $data, true);
+									$this->{$params['method']}($schema, $table_data, true);
 								}
 								else
 								{
-									$this->{$params['method']}($schema, $key, $data, true);
+									$this->{$params['method']}($schema, $table_name, $table_data, true);
 								}
 							}
 						}
@@ -274,10 +272,10 @@ class doctrine implements tools_interface, tools
 	 */
 	public function sql_create_table(string $table_name, array $table_data)
 	{
-		return $this->_alter_schema(
+		return $this->alter_schema(
 			function (Schema $schema) use ($table_name, $table_data): void
 			{
-				$this->_schema_create_table($schema, $table_name, $table_data, true);
+				$this->schema_create_table($schema, $table_name, $table_data, true);
 			}
 		);
 	}
@@ -287,10 +285,10 @@ class doctrine implements tools_interface, tools
 	 */
 	public function sql_table_drop(string $table_name)
 	{
-		return $this->_alter_schema(
+		return $this->alter_schema(
 			function (Schema $schema) use ($table_name): void
 			{
-				$this->_schema_drop_table($schema, $table_name, true);
+				$this->schema_drop_table($schema, $table_name, true);
 			}
 		);
 	}
@@ -300,10 +298,10 @@ class doctrine implements tools_interface, tools
 	 */
 	public function sql_column_add(string $table_name, string $column_name, array $column_data)
 	{
-		return $this->_alter_schema(
+		return $this->alter_schema(
 			function (Schema $schema) use ($table_name, $column_name, $column_data): void
 			{
-				$this->_schema_column_add($schema, $table_name, $column_name, $column_data);
+				$this->schema_column_add($schema, $table_name, $column_name, $column_data);
 			}
 		);
 	}
@@ -313,10 +311,10 @@ class doctrine implements tools_interface, tools
 	 */
 	public function sql_column_change(string $table_name, string $column_name, array $column_data)
 	{
-		return $this->_alter_schema(
+		return $this->alter_schema(
 			function (Schema $schema) use ($table_name, $column_name, $column_data): void
 			{
-				$this->_schema_column_change($schema, $table_name, $column_name, $column_data);
+				$this->schema_column_change($schema, $table_name, $column_name, $column_data);
 			}
 		);
 	}
@@ -326,10 +324,10 @@ class doctrine implements tools_interface, tools
 	 */
 	public function sql_column_remove(string $table_name, string $column_name)
 	{
-		return $this->_alter_schema(
+		return $this->alter_schema(
 			function (Schema $schema) use ($table_name, $column_name): void
 			{
-				$this->_schema_column_remove($schema, $table_name, $column_name);
+				$this->schema_column_remove($schema, $table_name, $column_name);
 			}
 		);
 	}
@@ -339,10 +337,10 @@ class doctrine implements tools_interface, tools
 	 */
 	public function sql_create_index(string $table_name, string $index_name, $column)
 	{
-		return $this->_alter_schema(
+		return $this->alter_schema(
 			function (Schema $schema) use ($table_name, $index_name, $column): void
 			{
-				$this->_schema_create_index($column, $schema, $table_name, $index_name);
+				$this->schema_create_index($column, $schema, $table_name, $index_name);
 			}
 		);
 	}
@@ -352,10 +350,10 @@ class doctrine implements tools_interface, tools
 	 */
 	public function sql_index_drop(string $table_name, string $index_name)
 	{
-		return $this->_alter_schema(
+		return $this->alter_schema(
 			function (Schema $schema) use ($table_name, $index_name): void
 			{
-				$this->_schema_index_drop($schema, $table_name, $index_name);
+				$this->schema_index_drop($schema, $table_name, $index_name);
 			}
 		);
 	}
@@ -365,10 +363,10 @@ class doctrine implements tools_interface, tools
 	 */
 	public function sql_create_unique_index(string $table_name, string $index_name, $column)
 	{
-		return $this->_alter_schema(
+		return $this->alter_schema(
 			function (Schema $schema) use ($table_name, $index_name, $column): void
 			{
-				$this->_schema_create_unique_index($column, $schema, $table_name, $index_name);
+				$this->schema_create_unique_index($column, $schema, $table_name, $index_name);
 			}
 		);
 	}
@@ -378,10 +376,10 @@ class doctrine implements tools_interface, tools
 	 */
 	public function sql_create_primary_key(string $table_name, $column)
 	{
-		return $this->_alter_schema(
+		return $this->alter_schema(
 			function (Schema $schema) use ($table_name, $column): void
 			{
-				$this->_schema_create_primary_key($schema, $column, $table_name);
+				$this->schema_create_primary_key($schema, $column, $table_name);
 			}
 		);
 	}
@@ -458,7 +456,7 @@ class doctrine implements tools_interface, tools
 	 *
 	 * @return bool|string[]
 	 */
-	protected function _alter_schema(callable $callback)
+	protected function alter_schema(callable $callback)
 	{
 		try
 		{
@@ -514,7 +512,7 @@ class doctrine implements tools_interface, tools
 	 *
 	 * @throws SchemaException
 	 */
-	protected function _schema_create_table(Schema $schema, string $table_name, array $table_data, bool $safe_check = false): void
+	protected function schema_create_table(Schema $schema, string $table_name, array $table_data, bool $safe_check = false): void
 	{
 		if ($safe_check && $this->sql_table_exists($table_name))
 		{
@@ -585,7 +583,7 @@ class doctrine implements tools_interface, tools
 	 *
 	 * @throws SchemaException
 	 */
-	protected function _schema_drop_table(Schema $schema, string $table_name, bool $safe_check = false): void
+	protected function schema_drop_table(Schema $schema, string $table_name, bool $safe_check = false): void
 	{
 		if ($safe_check && !$schema->hasTable($table_name))
 		{
@@ -604,7 +602,7 @@ class doctrine implements tools_interface, tools
 	 *
 	 * @throws SchemaException
 	 */
-	protected function _schema_column_add(Schema $schema, string $table_name, string $column_name, array $column_data, bool $safe_check = false): void
+	protected function schema_column_add(Schema $schema, string $table_name, string $column_name, array $column_data, bool $safe_check = false): void
 	{
 		$this->alter_table(
 			$schema,
@@ -634,7 +632,7 @@ class doctrine implements tools_interface, tools
 	 *
 	 * @throws SchemaException
 	 */
-	protected function _schema_column_change(Schema $schema, string $table_name, string $column_name, array $column_data, bool $safe_check = false): void
+	protected function schema_column_change(Schema $schema, string $table_name, string $column_name, array $column_data, bool $safe_check = false): void
 	{
 		$this->alter_table(
 			$schema,
@@ -659,7 +657,7 @@ class doctrine implements tools_interface, tools
 					$index_columns = array_map('strtolower', $index->getUnquotedColumns());
 					if (array_search($column_name, $index_columns, true) !== false)
 					{
-						$this->_recreate_index($table, $index, $index_columns);
+						$this->recreate_index($table, $index, $index_columns);
 					}
 				}
 			}
@@ -675,16 +673,16 @@ class doctrine implements tools_interface, tools
 	 *
 	 * @throws SchemaException
 	 */
-	protected function _schema_column_change_add(Schema $schema, string $table_name, string $column_name, array $column_data, bool $safe_check = false): void
+	protected function schema_column_change_add(Schema $schema, string $table_name, string $column_name, array $column_data, bool $safe_check = false): void
 	{
 		$table = $schema->getTable($table_name);
 		if ($table->hasColumn($column_name))
 		{
-			$this->_schema_column_change($schema, $table_name, $column_name, $column_data, $safe_check);
+			$this->schema_column_change($schema, $table_name, $column_name, $column_data, $safe_check);
 		}
 		else
 		{
-			$this->_schema_column_add($schema, $table_name, $column_name, $column_data, $safe_check);
+			$this->schema_column_add($schema, $table_name, $column_name, $column_data, $safe_check);
 		}
 	}
 
@@ -696,7 +694,7 @@ class doctrine implements tools_interface, tools
 	 *
 	 * @throws SchemaException
 	 */
-	protected function _schema_column_remove(Schema $schema, string $table_name, string $column_name, bool $safe_check = false): void
+	protected function schema_column_remove(Schema $schema, string $table_name, string $column_name, bool $safe_check = false): void
 	{
 		$this->alter_table(
 			$schema,
@@ -731,7 +729,7 @@ class doctrine implements tools_interface, tools
 					if ($key !== false)
 					{
 						unset($index_columns[$key]);
-						$this->_recreate_index($table, $index, $index_columns);
+						$this->recreate_index($table, $index, $index_columns);
 					}
 				}
 				$table->dropColumn($column_name);
@@ -748,7 +746,7 @@ class doctrine implements tools_interface, tools
 	 *
 	 * @throws SchemaException
 	 */
-	protected function _schema_create_index($column, Schema $schema, string $table_name, string $index_name, bool $safe_check = false): void
+	protected function schema_create_index($column, Schema $schema, string $table_name, string $index_name, bool $safe_check = false): void
 	{
 		$columns = (is_array($column)) ? $column : [$column];
 		$table = $schema->getTable($table_name);
@@ -770,7 +768,7 @@ class doctrine implements tools_interface, tools
 	 *
 	 * @throws SchemaException
 	 */
-	protected function _schema_create_unique_index($column, Schema $schema, string $table_name, string $index_name, bool $safe_check = false): void
+	protected function schema_create_unique_index($column, Schema $schema, string $table_name, string $index_name, bool $safe_check = false): void
 	{
 		$columns = (is_array($column)) ? $column : [$column];
 		$table = $schema->getTable($table_name);
@@ -791,7 +789,7 @@ class doctrine implements tools_interface, tools
 	 *
 	 * @throws SchemaException
 	 */
-	protected function _schema_index_drop(Schema $schema, string $table_name, string $index_name, bool $safe_check = false): void
+	protected function schema_index_drop(Schema $schema, string $table_name, string $index_name, bool $safe_check = false): void
 	{
 		$table = $schema->getTable($table_name);
 
@@ -811,7 +809,7 @@ class doctrine implements tools_interface, tools
 	 *
 	 * @throws SchemaException
 	 */
-	protected function _schema_create_primary_key(Schema $schema, $column, string $table_name, bool $safe_check = false): void
+	protected function schema_create_primary_key(Schema $schema, $column, string $table_name, bool $safe_check = false): void
 	{
 		$columns = (is_array($column)) ? $column : [$column];
 		$table = $schema->getTable($table_name);
@@ -828,7 +826,7 @@ class doctrine implements tools_interface, tools
 	 *
 	 * @throws SchemaException
 	 */
-	protected function _recreate_index(Table $table, Index $index, array $new_columns): void
+	protected function recreate_index(Table $table, Index $index, array $new_columns): void
 	{
 		if ($index->isPrimary())
 		{
diff --git a/phpBB/phpbb/db/tools/tools.php b/phpBB/phpbb/db/tools/tools.php
index 822df4d6ca..5036f78dc4 100644
--- a/phpBB/phpbb/db/tools/tools.php
+++ b/phpBB/phpbb/db/tools/tools.php
@@ -19,6 +19,6 @@ namespace phpbb\db\tools;
 *
 * @deprecated 4.0.0-a1
 */
-interface tools extends tools_interface
+class tools extends doctrine
 {
 }
diff --git a/phpBB/phpbb/db/tools/tools_interface.php b/phpBB/phpbb/db/tools/tools_interface.php
index 717f2c5a4e..498a2a8828 100644
--- a/phpBB/phpbb/db/tools/tools_interface.php
+++ b/phpBB/phpbb/db/tools/tools_interface.php
@@ -4,7 +4,7 @@
  * This file is part of the phpBB Forum Software package.
  *
  * @copyright (c) phpBB Limited <https://www.phpbb.com>
- * @license       GNU General Public License, version 2 (GPL-2.0)
+ * @license GNU General Public License, version 2 (GPL-2.0)
  *
  * For full copyright and license information, please see
  * the docs/CREDITS.txt file.
diff --git a/phpBB/phpbb/di/container_builder.php b/phpBB/phpbb/di/container_builder.php
index 6631800a8a..cca641403b 100644
--- a/phpBB/phpbb/di/container_builder.php
+++ b/phpBB/phpbb/di/container_builder.php
@@ -13,7 +13,6 @@
 
 namespace phpbb\di;
 
-use phpbb\db\doctrine\connection_factory;
 use Symfony\Bridge\ProxyManager\LazyProxy\PhpDumper\ProxyDumper;
 use Symfony\Component\Config\ConfigCache;
 use Symfony\Component\Config\FileLocator;
@@ -51,16 +50,6 @@ class container_builder
 	 */
 	protected $container;
 
-	/**
-	 * @var \phpbb\db\driver\driver_interface
-	 */
-	protected $dbal_connection = null;
-
-	/**
-	 * @var \Doctrine\DBAL\Connection
-	 */
-	private $dbal_connection_doctrine;
-
 	/**
 	 * Indicates whether extensions should be used (default to true).
 	 *
@@ -579,24 +568,20 @@ class container_builder
 		$config_data = $this->config_php_file->get_all();
 		if (!empty($config_data))
 		{
-			if ($this->dbal_connection === null)
-			{
-				$dbal_driver_class = \phpbb\config_php_file::convert_30_dbms_to_31($this->config_php_file->get('dbms'));
-				/** @var \phpbb\db\driver\driver_interface $dbal_connection */
-				$this->dbal_connection = new $dbal_driver_class();
-				$this->dbal_connection->sql_connect(
-					$this->config_php_file->get('dbhost'),
-					$this->config_php_file->get('dbuser'),
-					$this->config_php_file->get('dbpasswd'),
-					$this->config_php_file->get('dbname'),
-					$this->config_php_file->get('dbport'),
-					false,
-					defined('PHPBB_DB_NEW_LINK') && PHPBB_DB_NEW_LINK
-				);
-				$this->dbal_connection_doctrine = connection_factory::get_connection($this->config_php_file);
-			}
-			$this->container->set('dbal.conn.driver', $this->dbal_connection);
-			$this->container->set('dbal.conn.doctrine', $this->dbal_connection_doctrine);
+			$dbal_driver_class = \phpbb\config_php_file::convert_30_dbms_to_31($this->config_php_file->get('dbms'));
+			/** @var \phpbb\db\driver\driver_interface $dbal_connection */
+			$dbal_connection = new $dbal_driver_class();
+			$dbal_connection->sql_connect(
+				$this->config_php_file->get('dbhost'),
+				$this->config_php_file->get('dbuser'),
+				$this->config_php_file->get('dbpasswd'),
+				$this->config_php_file->get('dbname'),
+				$this->config_php_file->get('dbport'),
+				false,
+				defined('PHPBB_DB_NEW_LINK') && PHPBB_DB_NEW_LINK
+			);
+			//$this->dbal_connection_doctrine = connection_factory::get_connection($this->config_php_file);
+			$this->container->set('dbal.conn.driver', $dbal_connection);
 		}
 	}
 
diff --git a/tests/dbal/db_tools_test.php b/tests/dbal/db_tools_test.php
index 186f016a1d..f6344abdb2 100644
--- a/tests/dbal/db_tools_test.php
+++ b/tests/dbal/db_tools_test.php
@@ -386,7 +386,7 @@ class phpbb_dbal_db_tools_test extends phpbb_database_test_case
 	public function test_perform_schema_changes_drop_columns()
 	{
 		$db_tools = $this->getMockBuilder('\phpbb\db\tools\doctrine')
-			->onlyMethods(array('sql_column_exists', '_schema_column_remove'))
+			->onlyMethods(array('sql_column_exists', 'schema_column_remove'))
 			->setConstructorArgs(array($this->doctrine_db))
 			->getMock();
 
@@ -397,7 +397,7 @@ class phpbb_dbal_db_tools_test extends phpbb_database_test_case
 			->will($this->returnValue(true));
 
 		// drop columns
-		$db_tools->expects($this->exactly(2))->method('_schema_column_remove')
+		$db_tools->expects($this->exactly(2))->method('schema_column_remove')
 			->withConsecutive(
 				[$this->isInstanceOf(Schema::class), 'existing_table', 'dropped_column_1', true],
 				[$this->isInstanceOf(Schema::class), 'existing_table', 'dropped_column_2', true]