<p>I was having a similar issue and found a solution that worked for my setup:  <a href="https://craftcms.stackexchange.com/a/9016/831">https://craftcms.stackexchange.com/a/9016/831</a></p>

CC BY-SA 3.0
2015-04-03T17:41:58.740Z
2015-04-03T17:41:58.740Z
2017-04-13T12:51:00.253Z
Aaron Berkowitz
<blockquote>
  <p>Cannot modify header information - headers already sent</p>
</blockquote>

<p>That error means that something, somewhere has already started outputting to the browser before Yii/Craft/PHP expected it to happen.</p>

<p>99% of the time, it's some whitespace or unintended character that got added to the beginning of one of Craft's files.</p>

<p>Try doing a fresh upload of all of Craft's files and see if that helps.</p>

CC BY-SA 3.0
2015-02-25T21:07:01.473Z
Hi Brad, thanks a lot for your answer. I already tried a completely fresh install in a new folder with a fresh db etc. The only files I touched were the craft/config/db.php and the public .htaccess for the standard index.php rewrite. Any other suggestions? Maybe it's an encoding issue?
Matthias Ott
CC BY-SA 3.0
2015-02-25T21:14:52.677Z
If you enable devMode, does any other helpful information get logged?
Brad Bell
CC BY-SA 3.0
2015-02-26T16:06:13.467Z
DevMode did not show anything of help – as far as I can tell. The only thing that worked was setting _display_errors_ to _Off_ in php.ini. Not my preferred solution, but it works for now…
Matthias Ott
CC BY-SA 3.0
2015-02-25T15:36:51.637Z
2015-02-25T15:36:51.637Z
Brad Bell
<p>After a fresh install of Craft on my localhost, two problems occur:</p>

<p>1) The modal window to upgrade Craft only says <em>"An unknown error occured."</em></p>

<p>2) <strong>Newly created singles are not editable</strong>, the edit pane stays empty with no input fields at all.</p>

<p>I looked into craft.log and there seems to be an issue with CHttpRequest.php, but I can't say if this is a local config problem or if it's a bug:</p>

<pre><code>******************************************************************************************************
2015/02/25 13:08:35 [error] [php] Cannot modify header information - headers already sent (/Users/me/Sites/test-dev-craft/app/framework/web/CHttpRequest.php:1392)
Stack trace:
#0 /Users/me/Sites/test-dev-craft/app/framework/web/CHttpRequest.php(1329): Craft\CookieCollection-&gt;remove()
#1 /Users/me/Sites/test-dev-craft/app/services/UserSessionService.php(1170): Craft\CookieCollection-&gt;add()
#2 /Users/me/Sites/test-dev-craft/app/framework/web/auth/CWebUser.php(203): Craft\UserSessionService-&gt;renewCookie()
#3 /Users/me/Sites/test-dev-craft/app/services/UserSessionService.php(91): Craft\UserSessionService-&gt;init()
#4 /Users/me/Sites/test-dev-craft/app/framework/base/CModule.php(387): Craft\UserSessionService-&gt;init()
#5 /Users/me/Sites/test-dev-craft/app/etc/web/WebApp.php(569): Craft\WebApp-&gt;getComponent()
#6 /Users/me/Sites/test-dev-craft/app/framework/base/CModule.php(103): Craft\WebApp-&gt;getComponent()
#7 /Users/me/Sites/test-dev-craft/app/etc/web/WebApp.php(160): Craft\WebApp-&gt;__get()
#8 /Users/me/Sites/test-dev-craft/app/framework/base/CApplication.php(180): Craft\WebApp-&gt;processRequest()
#9 /Users/me/Sites/test-dev-craft/app/index.php(62): Craft\WebApp-&gt;run()
#10 /Users/me/Sites/test.dev/index.php(19): require_once()
REQUEST_URI=/test.dev/index.php/admin/actions/tasks/getRunningTaskInfo
</code></pre>

<p>This is my local setup:</p>

<ul>
<li>Mac OS X 10.10.2</li>
<li>Apache/2.2.29 (Unix) DAV/2 mod_fastcgi/2.4.6 mod_ssl/2.2.29 OpenSSL/1.0.2</li>
<li>PHP Version 5.6.5</li>
<li>MySQL 5.6.22 - Homebrew</li>
</ul>

<p>Any help would be highly appreciated!</p>

CC BY-SA 3.0
2015-03-05T23:23:01.017Z
I've also had this problem, running from localhost. Mac OS X 10.10.3
PHP 5.6.1
Mysql 5.5.38
Chase Giunta
CC BY-SA 3.0
2015-03-09T23:30:19.083Z
I'm getting this error locally too. PHP 5.6
Seán O'Grady
<entries><control-panel><error><upgrades>
Content / fields of newly created single don't show up
# Content / fields of newly created single don't show up

(Asked by: username_0 on 2015-02-25)

After a fresh install of Craft on my localhost, two problems occur:
1) The modal window to upgrade Craft only says "An unknown error occured."
2) Newly created singles are not editable, the edit pane stays empty with no input fields at all.
I looked into craft.log and there seems to be an issue with CHttpRequest.php, but I can't say if this is a local config problem or if it's a bug:
******************************************************************************************************
2015/02/25 13:08:35 [error] [php] Cannot modify header information - headers already sent (/Users/me/Sites/test-dev-craft/app/framework/web/CHttpRequest.php:1392)
Stack trace:
#0 /Users/me/Sites/test-dev-craft/app/framework/web/CHttpRequest.php(1329): Craft\CookieCollection->remove()
#1 /Users/me/Sites/test-dev-craft/app/services/UserSessionService.php(1170): Craft\CookieCollection->add()
#2 /Users/me/Sites/test-dev-craft/app/framework/web/auth/CWebUser.php(203): Craft\UserSessionService->renewCookie()
#3 /Users/me/Sites/test-dev-craft/app/services/UserSessionService.php(91): Craft\UserSessionService->init()
#4 /Users/me/Sites/test-dev-craft/app/framework/base/CModule.php(387): Craft\UserSessionService->init()
#5 /Users/me/Sites/test-dev-craft/app/etc/web/WebApp.php(569): Craft\WebApp->getComponent()
#6 /Users/me/Sites/test-dev-craft/app/framework/base/CModule.php(103): Craft\WebApp->getComponent()
#7 /Users/me/Sites/test-dev-craft/app/etc/web/WebApp.php(160): Craft\WebApp->__get()
#8 /Users/me/Sites/test-dev-craft/app/framework/base/CApplication.php(180): Craft\WebApp->processRequest()
#9 /Users/me/Sites/test-dev-craft/app/index.php(62): Craft\WebApp->run()
#10 /Users/me/Sites/test.dev/index.php(19): require_once()
REQUEST_URI=/test.dev/index.php/admin/actions/tasks/getRunningTaskInfo

This is my local setup:

Mac OS X 10.10.2
Apache/2.2.29 (Unix) DAV/2 mod_fastcgi/2.4.6 mod_ssl/2.2.29 OpenSSL/1.0.2
PHP Version 5.6.5
MySQL 5.6.22 - Homebrew

Any help would be highly appreciated!

**Tags:** entries, control-panel, error, upgrades

> **Comments:**
> **username_1**: I've also had this problem, running from localhost. Mac OS X 10.10.3 PHP 5.6.1 Mysql 5.5.38  
> **username_2**: I'm getting this error locally too. PHP 5.6  

---

## 2 answers

### Answer by username_3 on 2015-04-03. Score: 2

I was having a similar issue and found a solution that worked for my setup: <https://craftcms.stackexchange.com/a/9016/831>


---

### Answer by username_4 on 2015-02-25. Score: 0

> Cannot modify header information - headers already sent

That error means that something, somewhere has already started outputting to the browser before Yii/Craft/PHP expected it to happen.

99% of the time, it's some whitespace or unintended character that got added to the beginning of one of Craft's files.

Try doing a fresh upload of all of Craft's files and see if that helps.

> **Comments:**
> **username_0**: Hi Brad, thanks a lot for your answer. I already tried a completely fresh install in a new folder with a fresh db etc. The only files I touched were the craft/config/db.php and the public .htaccess for the standard index.php rewrite. Any other suggestions? Maybe it's an encoding issue?  
> **username_4**: If you enable devMode, does any other helpful information get logged?  
> **username_0**: DevMode did not show anything of help – as far as I can tell. The only thing that worked was setting _display_errors_ to _Off_ in php.ini. Not my preferred solution, but it works for now…  

---

