diff --git a/src/Tokenizers/PHP.php b/src/Tokenizers/PHP.php
index 31f2450a76..e3610cab4a 100644
--- a/src/Tokenizers/PHP.php
+++ b/src/Tokenizers/PHP.php
@@ -1074,7 +1074,10 @@ function return types. We want to keep the parenthesis map clean,
                         }
                     }
 
-                    if (is_array($tokens[$x]) === false && $tokens[$x] === ':') {
+                    if (isset($tokens[$x]) === true
+                        && is_array($tokens[$x]) === false
+                        && $tokens[$x] === ':'
+                    ) {
                         $allowed = [
                             T_STRING       => T_STRING,
                             T_ARRAY        => T_ARRAY,