diff --git a/src/PhpWord/Shared/ZipArchive.php b/src/PhpWord/Shared/ZipArchive.php
index 7ef0889e..46d5c036 100644
--- a/src/PhpWord/Shared/ZipArchive.php
+++ b/src/PhpWord/Shared/ZipArchive.php
@@ -170,6 +170,8 @@ class ZipArchive
         $list = $this->zip->listContent();
         $listCount = count($list);
         $listIndex = -1;
+        $contents = null;
+
         for ($i = 0; $i < $listCount; ++$i) {
             if (strtolower($list[$i]["filename"]) == strtolower($fileName) ||
                 strtolower($list[$i]["stored_filename"]) == strtolower($fileName)) {
diff --git a/src/PhpWord/Writer/ODText/Content.php b/src/PhpWord/Writer/ODText/Content.php
index 0669bc41..7fc0d2df 100644
--- a/src/PhpWord/Writer/ODText/Content.php
+++ b/src/PhpWord/Writer/ODText/Content.php
@@ -39,6 +39,10 @@ class Content extends WriterPart
      */
     public function writeContent(PhpWord $phpWord = null)
     {
+        if (is_null($phpWord)) {
+            throw new Exception("No PhpWord assigned.");
+        }
+
         // Create XML writer
         $xmlWriter = $this->getXmlWriter();
 
diff --git a/src/PhpWord/Writer/ODText/Meta.php b/src/PhpWord/Writer/ODText/Meta.php
index d0d593e2..fc5314e9 100644
--- a/src/PhpWord/Writer/ODText/Meta.php
+++ b/src/PhpWord/Writer/ODText/Meta.php
@@ -24,6 +24,10 @@ class Meta extends WriterPart
      */
     public function writeMeta(PhpWord $phpWord = null)
     {
+        if (is_null($phpWord)) {
+            throw new Exception("No PhpWord assigned.");
+        }
+
         // Create XML writer
         $xmlWriter = $this->getXmlWriter();
 
diff --git a/src/PhpWord/Writer/ODText/Styles.php b/src/PhpWord/Writer/ODText/Styles.php
index fa81ea9e..8839f568 100644
--- a/src/PhpWord/Writer/ODText/Styles.php
+++ b/src/PhpWord/Writer/ODText/Styles.php
@@ -28,6 +28,10 @@ class Styles extends WriterPart
      */
     public function writeStyles(PhpWord $phpWord = null)
     {
+        if (is_null($phpWord)) {
+            throw new Exception("No PhpWord assigned.");
+        }
+
         // Create XML writer
         $xmlWriter = $this->getXmlWriter();
 
diff --git a/src/PhpWord/Writer/Word2007/ContentTypes.php b/src/PhpWord/Writer/Word2007/ContentTypes.php
index 9e6853d0..9a383e9b 100755
--- a/src/PhpWord/Writer/Word2007/ContentTypes.php
+++ b/src/PhpWord/Writer/Word2007/ContentTypes.php
@@ -66,12 +66,10 @@ class ContentTypes extends WriterPart
         $xmlWriter->startDocument('1.0', 'UTF-8', 'yes');
         $xmlWriter->startElement('Types');
         $xmlWriter->writeAttribute('xmlns', 'http://schemas.openxmlformats.org/package/2006/content-types');
-        foreach ($defaults as $key => $value)
-        {
+        foreach ($defaults as $key => $value) {
             $this->writeContentType($xmlWriter, true, $key, $value);
         }
-        foreach ($overrides as $key => $value)
-        {
+        foreach ($overrides as $key => $value) {
             $this->writeContentType($xmlWriter, false, $key, $value);
         }
         $xmlWriter->endElement();
diff --git a/src/PhpWord/Writer/Word2007/DocProps.php b/src/PhpWord/Writer/Word2007/DocProps.php
index ceb5db04..cfa238e5 100644
--- a/src/PhpWord/Writer/Word2007/DocProps.php
+++ b/src/PhpWord/Writer/Word2007/DocProps.php
@@ -21,6 +21,10 @@ class DocProps extends WriterPart
      */
     public function writeDocPropsApp(PhpWord $phpWord = null)
     {
+        if (is_null($phpWord)) {
+            throw new Exception("No PhpWord assigned.");
+        }
+
         // Create XML writer
         $xmlWriter = $this->getXmlWriter();
 
diff --git a/src/PhpWord/Writer/Word2007/Document.php b/src/PhpWord/Writer/Word2007/Document.php
index 8bf46a0b..499aad19 100644
--- a/src/PhpWord/Writer/Word2007/Document.php
+++ b/src/PhpWord/Writer/Word2007/Document.php
@@ -28,6 +28,10 @@ class Document extends Base
      */
     public function writeDocument(PhpWord $phpWord = null)
     {
+        if (is_null($phpWord)) {
+            throw new Exception("No PhpWord assigned.");
+        }
+
         // Create XML writer
         $xmlWriter = $this->getXmlWriter();