diff --git a/.idea/workspace.xml b/.idea/workspace.xml
index e8fa7f4..1c9cffb 100644
--- a/.idea/workspace.xml
+++ b/.idea/workspace.xml
@@ -2,9 +2,7 @@
 <project version="4">
   <component name="ChangeListManager">
     <list default="true" id="e7c9c2bb-66f1-4e37-904c-d33d8c113bde" name="Default" comment="">
-      <change type="NEW" beforePath="" afterPath="$PROJECT_DIR$/php/helper.php" />
-      <change type="MODIFICATION" beforePath="$PROJECT_DIR$/.idea/workspace.xml" afterPath="$PROJECT_DIR$/.idea/workspace.xml" />
-      <change type="MODIFICATION" beforePath="$PROJECT_DIR$/php/upload.php" afterPath="$PROJECT_DIR$/php/upload.php" />
+      <change type="MODIFICATION" beforePath="$PROJECT_DIR$/php/download.php" afterPath="$PROJECT_DIR$/php/download.php" />
     </list>
     <ignored path="calendarimporter.iws" />
     <ignored path=".idea/workspace.xml" />
@@ -25,18 +23,6 @@
   </component>
   <component name="FileEditorManager">
     <leaf SIDE_TABS_SIZE_LIMIT_KEY="300">
-      <file leaf-file-name="upload.php" pinned="false" current-in-tab="true">
-        <entry file="file://$PROJECT_DIR$/php/upload.php">
-          <provider selected="true" editor-type-id="text-editor">
-            <state relative-caret-position="360">
-              <caret line="24" column="38" selection-start-line="24" selection-start-column="38" selection-end-line="24" selection-end-column="38" />
-              <folding>
-                <element signature="e#6#905#0#PHP" expanded="true" />
-              </folding>
-            </state>
-          </provider>
-        </entry>
-      </file>
       <file leaf-file-name="module.calendar.php" pinned="false" current-in-tab="false">
         <entry file="file://$PROJECT_DIR$/php/module.calendar.php">
           <provider selected="true" editor-type-id="text-editor">
@@ -51,6 +37,30 @@
           </provider>
         </entry>
       </file>
+      <file leaf-file-name="upload.php" pinned="false" current-in-tab="false">
+        <entry file="file://$PROJECT_DIR$/php/upload.php">
+          <provider selected="true" editor-type-id="text-editor">
+            <state relative-caret-position="340">
+              <caret line="24" column="0" selection-start-line="24" selection-start-column="0" selection-end-line="29" selection-end-column="28" />
+              <folding>
+                <element signature="e#6#905#0#PHP" expanded="true" />
+              </folding>
+            </state>
+          </provider>
+        </entry>
+      </file>
+      <file leaf-file-name="download.php" pinned="false" current-in-tab="true">
+        <entry file="file://$PROJECT_DIR$/php/download.php">
+          <provider selected="true" editor-type-id="text-editor">
+            <state relative-caret-position="345">
+              <caret line="46" column="23" selection-start-line="46" selection-start-column="13" selection-end-line="46" selection-end-column="23" />
+              <folding>
+                <element signature="e#7#908#0#PHP" expanded="true" />
+              </folding>
+            </state>
+          </provider>
+        </entry>
+      </file>
       <file leaf-file-name="helper.php" pinned="false" current-in-tab="false">
         <entry file="file://$PROJECT_DIR$/php/helper.php">
           <provider selected="true" editor-type-id="text-editor">
@@ -84,7 +94,6 @@
         <option value="$PROJECT_DIR$/changelog.txt" />
         <option value="$PROJECT_DIR$/Makefile" />
         <option value="$PROJECT_DIR$/manifest.xml" />
-        <option value="$PROJECT_DIR$/php/download.php" />
         <option value="$PROJECT_DIR$/php/plugin.calendarimporter.php" />
         <option value="$PROJECT_DIR$/build.xml" />
         <option value="$PROJECT_DIR$/js/ABOUT.js" />
@@ -107,6 +116,7 @@
         <option value="$PROJECT_DIR$/php/Helper.php" />
         <option value="$PROJECT_DIR$/php/helper.php" />
         <option value="$PROJECT_DIR$/php/upload.php" />
+        <option value="$PROJECT_DIR$/php/download.php" />
       </list>
     </option>
   </component>
@@ -270,12 +280,12 @@
       <option name="presentableId" value="Default" />
       <updated>1477949602474</updated>
       <workItem from="1477949603566" duration="9204000" />
-      <workItem from="1480441197414" duration="6911000" />
+      <workItem from="1480441197414" duration="7267000" />
     </task>
     <servers />
   </component>
   <component name="TimeTrackingManager">
-    <option name="totallyTimeSpent" value="16115000" />
+    <option name="totallyTimeSpent" value="16471000" />
   </component>
   <component name="ToolWindowManager">
     <frame x="65" y="24" width="1792" height="999" extended-state="6" />
@@ -640,12 +650,12 @@
         </state>
       </provider>
     </entry>
-    <entry file="file://$PROJECT_DIR$/php/download.php">
+    <entry file="file://$PROJECT_DIR$/php/helper.php">
       <provider selected="true" editor-type-id="text-editor">
-        <state relative-caret-position="75">
-          <caret line="23" column="26" selection-start-line="23" selection-start-column="10" selection-end-line="23" selection-end-column="26" />
+        <state relative-caret-position="690">
+          <caret line="56" column="41" selection-start-line="56" selection-start-column="41" selection-end-line="56" selection-end-column="41" />
           <folding>
-            <element signature="e#7#908#0#PHP" expanded="true" />
+            <element signature="e#6#905#0#PHP" expanded="true" />
           </folding>
         </state>
       </provider>
@@ -662,22 +672,22 @@
         </state>
       </provider>
     </entry>
-    <entry file="file://$PROJECT_DIR$/php/helper.php">
+    <entry file="file://$PROJECT_DIR$/php/upload.php">
       <provider selected="true" editor-type-id="text-editor">
-        <state relative-caret-position="690">
-          <caret line="56" column="41" selection-start-line="56" selection-start-column="41" selection-end-line="56" selection-end-column="41" />
+        <state relative-caret-position="340">
+          <caret line="24" column="0" selection-start-line="24" selection-start-column="0" selection-end-line="29" selection-end-column="28" />
           <folding>
             <element signature="e#6#905#0#PHP" expanded="true" />
           </folding>
         </state>
       </provider>
     </entry>
-    <entry file="file://$PROJECT_DIR$/php/upload.php">
+    <entry file="file://$PROJECT_DIR$/php/download.php">
       <provider selected="true" editor-type-id="text-editor">
-        <state relative-caret-position="360">
-          <caret line="24" column="38" selection-start-line="24" selection-start-column="38" selection-end-line="24" selection-end-column="38" />
+        <state relative-caret-position="345">
+          <caret line="46" column="23" selection-start-line="46" selection-start-column="13" selection-end-line="46" selection-end-column="23" />
           <folding>
-            <element signature="e#6#905#0#PHP" expanded="true" />
+            <element signature="e#7#908#0#PHP" expanded="true" />
           </folding>
         </state>
       </provider>
diff --git a/php/download.php b/php/download.php
index 75829ef..749c8c7 100644
--- a/php/download.php
+++ b/php/download.php
@@ -27,6 +27,7 @@ class DownloadHandler
 {
     /**
      * Download the given vcf file.
+     * @return boolean
      */
     public static function doDownload()
     {
@@ -43,7 +44,7 @@ class DownloadHandler
         }
 
         // validate token
-        if (!ctype_alnum($token)) { // token is a md5 hash
+        if (!preg_match('/^[a-zA-Z0-9]+$/', $token)) { // token is a md5 hash
             return false;
         }
 
@@ -69,5 +70,7 @@ class DownloadHandler
         readfile($file);
         ignore_user_abort(true);
         unlink($file);
+
+        return true;
     }
 }
\ No newline at end of file