From 48bc421e8154d53c67aa2e60c250da8fa668ad4e Mon Sep 17 00:00:00 2001
From: Eric Lippmann <eric.lippmann@icinga.com>
Date: Mon, 27 Jul 2026 11:23:19 +0200
Subject: [PATCH] Treat NUL bytes as empty in `Str::isEmpty()`

NUL bytes are invisible but fell outside the accepted empty character set.
This also caused combinations of NUL bytes and whitespace to be considered
nonempty.
---
 src/Str.php       |  6 +++---
 tests/StrTest.php | 10 ++++++++++
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/src/Str.php b/src/Str.php
index c7ab22b..2e23fd8 100644
--- a/src/Str.php
+++ b/src/Str.php
@@ -96,8 +96,8 @@ public static function trimSplit(?string $subject, string $delimiter = ',', ?int
     /**
      * Check if the given string is empty
      *
-     * Null is considered empty, and strings consisting only of whitespace or visually
-     * empty characters are considered empty.
+     * Null is considered empty, and strings consisting only of whitespace, NUL bytes,
+     * or visually empty characters are considered empty.
      *
      * @param string|Stringable|null $subject
      *
@@ -105,6 +105,6 @@ public static function trimSplit(?string $subject, string $delimiter = ',', ?int
      */
     public static function isEmpty(string|Stringable|null $subject): bool
     {
-        return $subject === null || preg_match('/^[\s\x{3164}\x{1160}]*$/u', $subject) === 1;
+        return $subject === null || preg_match('/^[\s\x00\x{3164}\x{1160}]*$/u', $subject) === 1;
     }
 }
diff --git a/tests/StrTest.php b/tests/StrTest.php
index bcff7db..8347d12 100644
--- a/tests/StrTest.php
+++ b/tests/StrTest.php
@@ -67,6 +67,16 @@ public function testIsEmptyReturnsTrueForStringWithOnlyWhitespace()
         $this->assertTrue(Str::isEmpty("\t\n"));
     }
 
+    public function testIsEmptyReturnsTrueForNulByte()
+    {
+        $this->assertTrue(Str::isEmpty("\0"));
+    }
+
+    public function testIsEmptyReturnsTrueForNulByteCombinedWithWhitespace()
+    {
+        $this->assertTrue(Str::isEmpty("\0 "));
+    }
+
     public function testIsEmptyReturnsFalseForZero()
     {
         $this->assertFalse(Str::isEmpty('0'));