diff --git a/src/Cite.php b/src/Cite.php
index 77487608e..6c50ae89f 100644
--- a/src/Cite.php
+++ b/src/Cite.php
@@ -291,9 +291,7 @@ class Cite {
 		);
 		$arguments = $status->getValue();
 		// Use the default group, or the references group when inside one.
-		if ( $arguments['group'] === null ) {
-			$arguments['group'] = $this->inReferencesGroup ?? self::DEFAULT_GROUP;
-		}
+		$arguments['group'] ??= $this->inReferencesGroup ?? self::DEFAULT_GROUP;
 
 		// @phan-suppress-next-line PhanParamTooFewUnpack No good way to document it.
 		$status->merge( $this->validateRef( $text, ...array_values( $arguments ) ) );
diff --git a/src/Hooks/CiteParserTagHooks.php b/src/Hooks/CiteParserTagHooks.php
index 32f9884f0..bb7c3bc00 100644
--- a/src/Hooks/CiteParserTagHooks.php
+++ b/src/Hooks/CiteParserTagHooks.php
@@ -90,9 +90,7 @@ class CiteParserTagHooks {
 	 * @return Cite
 	 */
 	private static function citeForParser( Parser $parser ): Cite {
-		if ( !isset( $parser->extCite ) ) {
-			$parser->extCite = new Cite( $parser );
-		}
+		$parser->extCite ??= new Cite( $parser );
 		return $parser->extCite;
 	}
 
diff --git a/src/ReferenceStack.php b/src/ReferenceStack.php
index 30d7d75b8..53480da15 100644
--- a/src/ReferenceStack.php
+++ b/src/ReferenceStack.php
@@ -111,12 +111,8 @@ class ReferenceStack {
 		?string $follow,
 		?string $dir
 	): ?array {
-		if ( !isset( $this->refs[$group] ) ) {
-			$this->refs[$group] = [];
-		}
-		if ( !isset( $this->groupRefSequence[$group] ) ) {
-			$this->groupRefSequence[$group] = 0;
-		}
+		$this->refs[$group] ??= [];
+		$this->groupRefSequence[$group] ??= 0;
 
 		$ref = [
 			'count' => $name ? 0 : -1,
@@ -403,11 +399,8 @@ class ReferenceStack {
 	 * @param string $text
 	 */
 	public function appendText( string $group, string $name, string $text ) {
-		if ( isset( $this->refs[$group][$name]['text'] ) ) {
-			$this->refs[$group][$name]['text'] .= $text;
-		} else {
-			$this->refs[$group][$name]['text'] = $text;
-		}
+		$this->refs[$group][$name]['text'] ??= '';
+		$this->refs[$group][$name]['text'] .= $text;
 	}
 
 }
diff --git a/src/ReferencesFormatter.php b/src/ReferencesFormatter.php
index 06b9288ef..97597a992 100644
--- a/src/ReferencesFormatter.php
+++ b/src/ReferencesFormatter.php
@@ -264,13 +264,11 @@ class ReferencesFormatter {
 	private function referencesFormatEntryAlternateBacklinkLabel(
 		Parser $parser, int $offset
 	): string {
-		if ( $this->backlinkLabels === null ) {
-			$this->backlinkLabels = preg_split(
-				'/\s+/',
-				$this->messageLocalizer->msg( 'cite_references_link_many_format_backlink_labels' )
-					->plain()
-			);
-		}
+		$this->backlinkLabels ??= preg_split(
+			'/\s+/',
+			$this->messageLocalizer->msg( 'cite_references_link_many_format_backlink_labels' )
+				->plain()
+		);
 
 		return $this->backlinkLabels[$offset]
 			?? $this->errorReporter->plain( $parser, 'cite_error_references_no_backlink_label' );
diff --git a/src/ResourceLoader/CitationToolDefinition.php b/src/ResourceLoader/CitationToolDefinition.php
index 9b5f1625b..b6ac23b83 100644
--- a/src/ResourceLoader/CitationToolDefinition.php
+++ b/src/ResourceLoader/CitationToolDefinition.php
@@ -24,26 +24,22 @@ class CitationToolDefinition {
 				->plain()
 		);
 
-		if ( $citationDefinition === null ) {
-			$citationDefinition = json_decode(
-				$context->msg( 'visualeditor-cite-tool-definition.json' )
-					->inContentLanguage()
-					->plain()
-			);
-		}
+		$citationDefinition ??= json_decode(
+			$context->msg( 'visualeditor-cite-tool-definition.json' )
+				->inContentLanguage()
+				->plain()
+		);
 
 		$citationTools = [];
 		if ( is_array( $citationDefinition ) ) {
 			foreach ( $citationDefinition as $tool ) {
-				if ( !isset( $tool->title ) ) {
-					// The following messages are generated here:
-					// * visualeditor-cite-tool-name-book
-					// * visualeditor-cite-tool-name-journal
-					// * visualeditor-cite-tool-name-news
-					// * visualeditor-cite-tool-name-web
-					$tool->title = $context->msg( 'visualeditor-cite-tool-name-' . $tool->name )
-						->text();
-				}
+				// The following messages are generated here:
+				// * visualeditor-cite-tool-name-book
+				// * visualeditor-cite-tool-name-journal
+				// * visualeditor-cite-tool-name-news
+				// * visualeditor-cite-tool-name-web
+				$tool->title ??= $context->msg( 'visualeditor-cite-tool-name-' . $tool->name )
+					->text();
 				$citationTools[] = $tool;
 			}
 		}
diff --git a/tests/phpunit/unit/CiteParserHooksTest.php b/tests/phpunit/unit/CiteParserHooksTest.php
index 7911efacd..dc10cde4b 100644
--- a/tests/phpunit/unit/CiteParserHooksTest.php
+++ b/tests/phpunit/unit/CiteParserHooksTest.php
@@ -43,7 +43,7 @@ class CiteParserHooksTest extends \MediaWikiUnitTestCase {
 		$citeParserHooks = new CiteParserHooks();
 		$citeParserHooks->onParserClearState( $parser );
 
-		$this->assertFalse( isset( $parser->extCite ) );
+		$this->assertObjectNotHasProperty( 'extCite', $parser );
 	}
 
 	/**
@@ -56,7 +56,7 @@ class CiteParserHooksTest extends \MediaWikiUnitTestCase {
 		$citeParserHooks = new CiteParserHooks();
 		$citeParserHooks->onParserCloned( $parser );
 
-		$this->assertFalse( isset( $parser->extCite ) );
+		$this->assertObjectNotHasProperty( 'extCite', $parser );
 	}
 
 	/**
diff --git a/tests/phpunit/unit/ReferencesFormatterTest.php b/tests/phpunit/unit/ReferencesFormatterTest.php
index 2d6a6688b..7f5ece973 100644
--- a/tests/phpunit/unit/ReferencesFormatterTest.php
+++ b/tests/phpunit/unit/ReferencesFormatterTest.php
@@ -370,16 +370,13 @@ class ReferencesFormatterTest extends \MediaWikiUnitTestCase {
 		$mockMessageLocalizer->method( 'msg' )
 			->willReturn( $mockMessage );
 
-		$mockErrorReporter = $this->createMock( ErrorReporter::class );
-		if ( $expectedLabel === null ) {
-			$mockErrorReporter->expects( $this->once() )->method( 'plain' );
-		} else {
-			$mockErrorReporter->expects( $this->never() )->method( 'plain' );
-		}
+		$errorReporter = $this->createMock( ErrorReporter::class );
+		$errorReporter->expects( $expectedLabel ? $this->never() : $this->once() )
+			->method( 'plain' );
 
 		/** @var ReferencesFormatter $formatter */
 		$formatter = TestingAccessWrapper::newFromObject( new ReferencesFormatter(
-			$mockErrorReporter,
+			$errorReporter,
 			$this->createMock( AnchorFormatter::class ),
 			$mockMessageLocalizer
 		) );