title: Why does array_diff on arrays of arrays return an empty array?
body: <p>I've got two arrays, for which var_dump give the following values:</p>
  
  <p>$array1:</p>
  
  <pre><code>Artifacts:array(2) { [0]=&gt;  array(3) { [0]=&gt;  string(7) "module1" [1]=&gt;  string(16) "path/to/file.txt" [2]=&gt;  string(0) "" } [1]=&gt;  array(3) { [0]=&gt;  string(7) "module2" [1]=&gt;  string(17) "path/to/file2.txt" [2]=&gt;  string(0) "" } }
  </code></pre>
  
  <p>$array2:</p>
  
  <pre><code>Artifacts:array(1) { [0]=&gt;  array(3) { [0]=&gt;  string(7) "module1" [1]=&gt;  string(16) "path/to/file.txt" [2]=&gt;  string(0) "" } }
  </code></pre>
  
  <p>I would think that doing <code>array_diff($array1,$array2)</code> would give me an array countaining only the second elements. Instead I got an empty array. I try switching the parameters, and still an empty_array, but this time without surprise. Wouldn't <code>array_diff</code> work on arrays of arrays? </p>