Escape control characters in cell values

Control characters in cell values are automatically escaped without
the need to excplicitly call `StringHelper::buildCharacterSets()` beforehand.

Fixes #212

CHANGELOG.md

@@ -17,6 +17,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ### Fixed
 
+- Control characters in cell values are automatically escaped [#212](https://github.com/PHPOffice/PhpSpreadsheet/issues/212)
+
 ### BREAKING CHANGE
 
 - Standardization of array keys used for style, see the [migration guide](./docs/topics/migration-from-PHPExcel.md).

src/PhpSpreadsheet/Shared/StringHelper.php

@@ -300,11 +300,12 @@ class StringHelper
         return true;
     }
 
-    public static function buildCharacterSets()
+    private static function buildCharacterSets()
     {
         if (empty(self::$controlCharacters)) {
             self::buildControlCharacters();
         }
+
         if (empty(self::$SYLKCharacters)) {
             self::buildSYLKCharacters();
         }
@@ -327,6 +328,8 @@ class StringHelper
      */
     public static function controlCharacterOOXML2PHP($value)
     {
+        self::buildCharacterSets();
+
         return str_replace(array_keys(self::$controlCharacters), array_values(self::$controlCharacters), $value);
     }
 
@@ -347,6 +350,8 @@ class StringHelper
      */
     public static function controlCharacterPHP2OOXML($value)
     {
+        self::buildCharacterSets();
+
         return str_replace(array_values(self::$controlCharacters), array_keys(self::$controlCharacters), $value);
     }
 
@@ -713,6 +718,8 @@ class StringHelper
      */
     public static function SYLKtoUTF8($pValue)
     {
+        self::buildCharacterSets();
+
         // If there is no escape character in the string there is nothing to do
         if (strpos($pValue, '') === false) {
             return $pValue;

tests/PhpSpreadsheetTests/Shared/StringHelperTest.php

@@ -5,7 +5,7 @@ namespace PhpOffice\PhpSpreadsheetTests\Shared;
 use PhpOffice\PhpSpreadsheet\Shared\StringHelper;
 use PHPUnit_Framework_TestCase;
 
-class StringTest extends PHPUnit_Framework_TestCase
+class StringHelperTest extends PHPUnit_Framework_TestCase
 {
     public function setUp()
     {
@@ -73,4 +73,28 @@ class StringTest extends PHPUnit_Framework_TestCase
         $result = StringHelper::getCurrencyCode();
         $this->assertEquals($expectedResult, $result);
     }
+
+    public function testControlCharacterPHP2OOXML()
+    {
+        $expectedResult = 'foo_x000B_bar';
+        $result = StringHelper::controlCharacterPHP2OOXML('foo' . chr(11) . 'bar');
+
+        $this->assertEquals($expectedResult, $result);
+    }
+
+    public function testControlCharacterOOXML2PHP()
+    {
+        $expectedResult = 'foo' . chr(11) . 'bar';
+        $result = StringHelper::controlCharacterOOXML2PHP('foo_x000B_bar');
+
+        $this->assertEquals($expectedResult, $result);
+    }
+
+    public function testSYLKtoUTF8()
+    {
+        $expectedResult = 'foo' . chr(11) . 'bar';
+        $result = StringHelper::SYLKtoUTF8("foo\x1B ;bar");
+
+        $this->assertEquals($expectedResult, $result);
+    }
 }