title: is there any algorithm which can find arrays which do not have common key between them
body: <pre><code>$array1 = array (
      '1' =&gt; A,
      '2' =&gt; B,
      '3' =&gt; C
  );
  
  $array2 = array (
      '1' =&gt; A,
      '4' =&gt; B,
      '5' =&gt; D
  );
  
  $array3 = array (
      '5' =&gt; A,
      '6' =&gt; E,
      '7' =&gt; D
  );
  
  $array4 = array (
      '4' =&gt; A,
      '7' =&gt; B,
      '10' =&gt; C
  );
  </code></pre>
  
  <p>I want to find out arrays which has all different keys, not a single key should be common between arrays. </p>
  
  <p><code>$array1 - $array3, $array1 - $array4</code> are two combinations which do not have common keys. Output of algorithm should be these combinations.</p>