Add sanity check when detecting token type

Fixes https://github.com/phpmyadmin/phpmyadmin/issues/13483

Signed-off-by: Michal Čihař <michal@cihar.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/src/Context.php b/src/Context.php
index 545bf08..fd8d96a 100644
--- a/src/Context.php
+++ b/src/Context.php
@@ -310,6 +310,9 @@ abstract class Context
     public static function isComment($str, $end=false)
     {
         $len = strlen($str);
+        if ($len == 0) {
+            return null;
+        }
         if ($str[0] === '#') {
             return Token::FLAG_COMMENT_BASH;
         } elseif (($len > 1) && ($str[0] === '/') && ($str[1] === '*')) {
@@ -376,6 +379,9 @@ abstract class Context
      */
     public static function isSymbol($str)
     {
+        if (strlen($str) == 0) {
+            return null;
+        }
         if ($str[0] === '@') {
             return Token::FLAG_SYMBOL_VARIABLE;
         } elseif ($str[0] === '`') {
@@ -397,6 +403,9 @@ abstract class Context
      */
     public static function isString($str)
     {
+        if (strlen($str) == 0) {
+            return null;
+        }
         if ($str[0] === '\'') {
             return Token::FLAG_STRING_SINGLE_QUOTES;
         } elseif ($str[0] === '"') {