length arg of byteSubstr is now optional

framework/CHANGELOG.md

@@ -82,6 +82,7 @@ Yii Framework 2 Change Log
 - Bug: URL encoding for the route parameter added to `\yii\web\UrlManager` (klimov-paul)
 - Bug: Fixed the bug that requesting protected or private action methods would cause 500 error instead of 404 (qiangxue)
 - Bug: Fixed Object of class Imagick could not be converted to string in CaptchaAction (eXprojects, cebe)
+- Bug: Fixed wrong behavior of `StringHelper::byteSubstr()` in some edge cases (cebe)
 - Enh #87: Helper `yii\helpers\Security` converted into application component, cryptographic strength improved (klimov-paul)
 - Enh #422: Added Support for BIT(M) data type default values in Schema (cebe)
 - Enh #1160: Added $strict parameter to Inflector::camel2id() to handle consecutive uppercase chars (schmunk)

framework/helpers/BaseStringHelper.php

@@ -34,13 +34,14 @@ class BaseStringHelper
      * This method ensures the string is treated as a byte array by using `mb_substr()`.
      * @param string $string the input string. Must be one character or longer.
      * @param integer $start the starting position
-     * @param integer $length the desired portion length
+     * @param integer $length the desired portion length. If not specified or `null`, there will be
+     * no limit on length i.e. the output will be until the end of the string.
      * @return string the extracted part of string, or FALSE on failure or an empty string.
      * @see http://www.php.net/manual/en/function.substr.php
      */
-    public static function byteSubstr($string, $start, $length)
+    public static function byteSubstr($string, $start, $length = null)
     {
-        return mb_substr($string, $start, $length ?: mb_strlen($string, '8bit'), '8bit');
+        return mb_substr($string, $start, $length === null ? mb_strlen($string, '8bit') : $length, '8bit');
     }
 
     /**

tests/unit/framework/helpers/StringHelperTest.php

@@ -26,6 +26,34 @@ class StringHelperTest extends TestCase
     {
         $this->assertEquals('th', StringHelper::byteSubstr('this', 0, 2));
         $this->assertEquals('э', StringHelper::byteSubstr('это', 0, 2));
+
+        $this->assertEquals('abcdef', StringHelper::byteSubstr('abcdef', 0));
+        $this->assertEquals('abcdef', StringHelper::byteSubstr('abcdef', 0, null));
+
+        $this->assertEquals('de',     StringHelper::byteSubstr('abcdef', 3, 2));
+        $this->assertEquals('def',    StringHelper::byteSubstr('abcdef', 3));
+        $this->assertEquals('def',    StringHelper::byteSubstr('abcdef', 3, null));
+
+        $this->assertEquals('cd',     StringHelper::byteSubstr('abcdef', -4, 2));
+        $this->assertEquals('cdef',   StringHelper::byteSubstr('abcdef', -4));
+        $this->assertEquals('cdef',   StringHelper::byteSubstr('abcdef', -4, null));
+
+        $this->assertEquals('',   StringHelper::byteSubstr('abcdef', 4, 0));
+        $this->assertEquals('',   StringHelper::byteSubstr('abcdef', -4, 0));
+
+        $this->assertEquals('это', StringHelper::byteSubstr('это', 0));
+        $this->assertEquals('это', StringHelper::byteSubstr('это', 0, null));
+
+        $this->assertEquals('т',     StringHelper::byteSubstr('это', 2, 2));
+        $this->assertEquals('то',    StringHelper::byteSubstr('это', 2));
+        $this->assertEquals('то',    StringHelper::byteSubstr('это', 2, null));
+
+        $this->assertEquals('т',     StringHelper::byteSubstr('это', -4, 2));
+        $this->assertEquals('то',   StringHelper::byteSubstr('это', -4));
+        $this->assertEquals('то',   StringHelper::byteSubstr('это', -4, null));
+
+        $this->assertEquals('',   StringHelper::byteSubstr('это', 4, 0));
+        $this->assertEquals('',   StringHelper::byteSubstr('это', -4, 0));
     }
 
     public function testBasename()