title: Interpolation (double quoted string) of Associative Arrays in PHP
body: <p>When interpolating PHP's string-indexed array elements (5.3.3, Win32)
  the following behavior may be expected or not:</p>
  
  <pre><code>$ha = array('key1' =&gt; 'Hello to me');
  
  print $ha['key1'];   # correct (usual way)
  print $ha[key1];     # Warning, works (use of undefined constant)
  
  print "He said {$ha['key1']}"; # correct (usual way)
  print "He said {$ha[key1]}";   # Warning, works (use of undefined constant)
  
  print "He said $ha['key1']";   # Error, unexpected T_ENCAPSED_AND_WHITESPACE
  print "He said $ha[ key1 ]";   # Error, unexpected T_ENCAPSED_AND_WHITESPACE
  print "He said $ha[key1]";     # !! correct (How Comes?)
  </code></pre>
  
  <p>Inerestingly, <strong>the last line seems to be correct PHP code</strong>. Any explanations?
  Can this feature be trusted?</p>
  
  <p><hr>
  Edit: The point of the posting now set in <strong>bold face</strong> in order to reduce misunderstandings.</p>