diff --git a/common/framework/parsers/DBQueryParser.php b/common/framework/parsers/DBQueryParser.php
index 59740bd56..f5aaf169c 100644
--- a/common/framework/parsers/DBQueryParser.php
+++ b/common/framework/parsers/DBQueryParser.php
@@ -11,15 +11,15 @@ class DBQueryParser extends BaseParser
 	 * Load a query XML file.
 	 *
 	 * @param string $filename
-	 * @return object|false
+	 * @return ?object
 	 */
-	public static function loadXML(string $filename)
+	public static function loadXML(string $filename): ?object
 	{
 		// Load the XML file.
 		$xml = simplexml_load_string(file_get_contents($filename));
 		if ($xml === false)
 		{
-			return false;
+			return null;
 		}
 
 		// Parse the query.
diff --git a/common/framework/parsers/DBTableParser.php b/common/framework/parsers/DBTableParser.php
index 1e9ff772e..8ba82b924 100644
--- a/common/framework/parsers/DBTableParser.php
+++ b/common/framework/parsers/DBTableParser.php
@@ -10,7 +10,7 @@ class DBTableParser extends BaseParser
 	/**
 	 * Mapping for XE-compatible types.
 	 */
-	protected static $_xe_types = array(
+	protected const XE_COMPAT_TYPES = array(
 		'bignumber' => 'bigint',
 		'number' => 'bigint',
 		'bigtext' => 'longtext',
@@ -20,7 +20,7 @@ class DBTableParser extends BaseParser
 	/**
 	 * List of types for which the size attribute will be ignored.
 	 */
-	protected static $_nosize_types = array(
+	protected const NO_SIZE_TYPES = array(
 		'bigint' => true,
 		'int' => true,
 		'integer' => true,
@@ -31,9 +31,9 @@ class DBTableParser extends BaseParser
 	 *
 	 * @param string $filename
 	 * @param string $content
-	 * @return object|false
+	 * @return ?object
 	 */
-	public static function loadXML(string $filename = '', string $content = '')
+	public static function loadXML(string $filename = '', string $content = ''): object
 	{
 		// Load the XML content.
 		if ($content)
@@ -47,7 +47,7 @@ class DBTableParser extends BaseParser
 
 		if ($xml === false)
 		{
-			return false;
+			return null;
 		}
 
 		// Initialize table definition.
@@ -225,10 +225,10 @@ class DBTableParser extends BaseParser
 	public static function getTypeAndSize(string $type, string $size): array
 	{
 		// Map XE-compatible types to database native types.
-		if (isset(self::$_xe_types[$type]))
+		if (isset(self::XE_COMPAT_TYPES[$type]))
 		{
 			$xetype = $type;
-			$type = self::$_xe_types[$type];
+			$type = self::XE_COMPAT_TYPES[$type];
 		}
 		else
 		{
@@ -243,7 +243,7 @@ class DBTableParser extends BaseParser
 			$size = $matches[2];
 		}
 		$size = implode(',', array_map('trim', explode(',', $size))) ?: null;
-		if (isset(self::$_nosize_types[$type]))
+		if (isset(self::NO_SIZE_TYPES[$type]))
 		{
 			$size = null;
 		}
diff --git a/common/framework/parsers/dbquery/Query.php b/common/framework/parsers/dbquery/Query.php
index 3b0e4e76a..705fe0762 100644
--- a/common/framework/parsers/dbquery/Query.php
+++ b/common/framework/parsers/dbquery/Query.php
@@ -99,7 +99,7 @@ class Query extends VariableBase
 	 *
 	 * @return array
 	 */
-	public function getQueryParams()
+	public function getQueryParams(): array
 	{
 		return $this->_params;
 	}
@@ -596,7 +596,7 @@ class Query extends VariableBase
 	/**
 	 * Generate a ORDER BY clause from navigation settings.
 	 *
-	 * @param object $navigation
+	 * @param Navigation $navigation
 	 * @return string
 	 */
 	protected function _arrangeOrderBy(Navigation $navigation): string
@@ -643,7 +643,7 @@ class Query extends VariableBase
 	/**
 	 * Generate a LIMIT/OFFSET clause from navigation settings.
 	 *
-	 * @param object $navigation
+	 * @param Navigation $navigation
 	 * @return string
 	 */
 	protected function _arrangeLimitOffset(Navigation $navigation): string
@@ -688,7 +688,7 @@ class Query extends VariableBase
 	/**
 	 * Generate each condition in a WHERE clause.
 	 *
-	 * @param object $condition
+	 * @param VariableBase $condition
 	 * @return string
 	 */
 	protected function _parseCondition(VariableBase $condition): string
@@ -736,7 +736,7 @@ class Query extends VariableBase
 	 * @param bool $allow_empty_string
 	 * @return bool
 	 */
-	public static function isValidVariable($var, $allow_empty_string = true): bool
+	public static function isValidVariable($var, bool $allow_empty_string = true): bool
 	{
 		if ($var === null || ($var === '' && !$allow_empty_string))
 		{
diff --git a/common/framework/parsers/dbquery/VariableBase.php b/common/framework/parsers/dbquery/VariableBase.php
index 335f1a4fd..e8e533ebb 100644
--- a/common/framework/parsers/dbquery/VariableBase.php
+++ b/common/framework/parsers/dbquery/VariableBase.php
@@ -284,7 +284,7 @@ class VariableBase
 	 * @param array $args
 	 * @return array
 	 */
-	public function getValue(array $args)
+	public function getValue(array $args): array
 	{
 		if ($this->var && Query::isValidVariable($args[$this->var] ?? null, $this instanceof ColumnWrite))
 		{
@@ -324,7 +324,7 @@ class VariableBase
 	 *
 	 * @return array
 	 */
-	public function getDefaultValue()
+	public function getDefaultValue(): array
 	{
 		// Get the current column name.
 		$column = $this instanceof ColumnWrite ? $this->name : ($this->column ?? null);
@@ -390,7 +390,7 @@ class VariableBase
 	 * @param mixed $value
 	 * @return void
 	 */
-	public function filterValue($value)
+	public function filterValue($value): void
 	{
 		// Don't apply a filter if there is no variable.
 		$column = $this instanceof ColumnWrite ? $this->name : $this->column;
@@ -465,7 +465,7 @@ class VariableBase
 	 * @param string $value
 	 * @return array
 	 */
-	protected function _parseSearchKeywords($column, $value)
+	protected function _parseSearchKeywords(string $column, string $value): array
 	{
 		// Initialze the return values.
 		$where = '';