diff --git a/VariableAnalysis/Sniffs/CodeAnalysis/VariableAnalysisSniff.php b/VariableAnalysis/Sniffs/CodeAnalysis/VariableAnalysisSniff.php
index d454e627..544e24ab 100644
--- a/VariableAnalysis/Sniffs/CodeAnalysis/VariableAnalysisSniff.php
+++ b/VariableAnalysis/Sniffs/CodeAnalysis/VariableAnalysisSniff.php
@@ -79,7 +79,7 @@ private function getPassByReferenceFunction(string $functionName) {
         $passByRefFunctions[$function] = explode(',', $args);
       }
     }
-    return $passByRefFunctions[$functionName] ?? null;
+    return isset($passByRefFunctions[$functionName]) ? $passByRefFunctions[$functionName] : null;
   }
 
   /**