title: array_unique for multidimensional arrays
body: <p>In case of one-dim array I can use <code>array_unique</code> to get unique entries. But which function should be used to work with two-dim arrays?
  For instance:</p>
  
  <pre><code>Array[0][0] = '123'; Array[0][1] = 'aaa';
  Array[1][0] = '124'; Array[1][1] = 'aaa';
  Array[2][0] = '124'; Array[2][1] = 'aaa';
  </code></pre>
  
  <p>In the above example I need to delete non-unique rows based on column 0. As a result I should get first two entries, while the third entry should be deleted. How to do this?</p>