title: Is en_UK an illegal locale?
body: <p>So far I had always used 'en_UK' for British English. Today I got an error when using it with Zend Framework because the locale is not included in the long list of recognized locales.</p>
  
  <p>Here's just a short extract of that list:</p>
  
  <pre><code>'ee_GH' =&gt; true, 'ee_TG' =&gt; true, 'ee'    =&gt; true, 'el_CY' =&gt; true, 'el_GR' =&gt; true,
  'el'    =&gt; true, 'en_AS' =&gt; true, 'en_AU' =&gt; true, 'en_BE' =&gt; true, 'en_BW' =&gt; true,
  'en_BZ' =&gt; true, 'en_CA' =&gt; true, 'en_GB' =&gt; true, 'en_GU' =&gt; true, 'en_HK' =&gt; true,
  'en_IE' =&gt; true, 'en_IN' =&gt; true, 'en_JM' =&gt; true, 'en_MH' =&gt; true, 'en_MP' =&gt; true,
  'en_MT' =&gt; true, 'en_NA' =&gt; true, 'en_NZ' =&gt; true, 'en_PH' =&gt; true, 'en_PK' =&gt; true,
  'en_SG' =&gt; true, 'en_TT' =&gt; true, 'en_UM' =&gt; true, 'en_US' =&gt; true, 'en_VI' =&gt; true,
  'en_ZA' =&gt; true, 'en_ZW' =&gt; true, 'en'    =&gt; true, 'eo'    =&gt; true, 'es_AR' =&gt; true,
  'es_BO' =&gt; true, 'es_CL' =&gt; true, 'es_CO' =&gt; true, 'es_CR' =&gt; true, 'es_DO' =&gt; true,
  </code></pre>
  
  <p>As you can see, there are all kinds of territories with English language and there is also an entry 'en_GB' which I assume stands for Great Britain... but there is no 'en_UK'. Is that just a 'bug' in Zend Framework or is there another reason for that?</p>