OpenCart: Headers already sent error

As it turns out, I keep on sharing the OpenCart errors that I come across every day. Well, I suppose that I’d like to save people the frustration and infinite reading on the problems that I’ve already got solved. So, I present to you OpenCart error of the week :-)

Warning: Cannot modify header information – headers already sent by (output started at ...) in ... on line ...

This is mostly intended for not-so-tech people, who are in a hurry to solve their OpenCart problem. That’s why  I will not get into the “Why” of the problem, but the “How”.

Tools you need

  1. An advanced text editor like Notepad++, SublimeText.
  2. Some patience. :-)


  1. First, let’s Look closely at the error message:
    Warning: Cannot modify header information - headers already sent by (output started at /home/mywebsite/public_html/catalog/language/thai/payment/bank_transfer.php:1) in/home/mywebsite/public_html/vqmod/vqcache/vq2-system_engine_controller.php

    Surely, you have noticed the pattern.

  2. Now, it’s time to hunt down that file. You need to open the file
    in the text editor.
  3. At the very beginning of the file, look for white spaces, like this
    and remove them. < must be the first symbol at the beginning of the file
  4. Look for white spaces at the end of the file, like this
    > must be the last symbol at the end the file.
  5. Then go to File->Save As… and choose UTF8 without BOM for encoding.
  6. Reupload the file in ASCII mode.

If this doesn’t solve the problem, it can be a conflicting vQmod extension. Disable all extensions and see when the problem appears again.

Still no luck?

Well, then I suppose you can dive in the sea of other solutions. These are nice guides:

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6 thoughts on “OpenCart: Headers already sent error”

    1. You’re welcome. Thought I’d share this, since it’s such a frustrating problem that seems to appear out of the blue…

  1. I had a problem with bulgarian translation of opencart – in my error folder file not_found was wrong encoded and this was cousing the “headers sent” error. Thanks for the help

  2. Hi Gergana,
    Having Cannot modify header information – headers already sent by (output started at , /xxx/xxxx/vqmod/vqcache/vq2-system_engine_controller.php on

    just cannot find the way out although the googling, removed all white spaces, it turned out problem is related with header(‘Status: ‘ . $status);
    header(‘Location: ‘ . str_replace(array(‘&’, “\n”, “\r”), array(‘&’, ”, ”), $url));

    Any help would be appreciated.

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