Description:
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I am using the following line in a script:

   header('Content-Language: '.$PAGE['lang']);

If $PAGE['lang'] is 'no' then the http header gets sent as expected:

   Content-Language: no

However when $PAGE['lang'] is 'en' (and it definately is just 'en' without any whitespace or uppercase characters) then this gets sent instead:

   Content-Language: en, en

Is this a bug or am I not understanding something? Or maybe something Apache's doing afterwards? (I have version 1.3.29)

I did some testing and it seems the first 'en' is my string and the second one is being added if that's of any help.


Reproduce code:
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// English
header('Content-Language: en');

// Norwegian
header('Content-Language: no');


Expected result:
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Content-Language: en
Content-Language: no

Actual result:
--------------
Content-Language: en, en
Content-Language: no