title: array_column not working for an array of objects?
body: <p>This is my current array structure:</p>
  
  <pre><code>array(2) {
    ["Ground"] =&gt; array(4) {
      [0] =&gt; object(Shipping\Model\Shipping)#337 (5) {
        ["shipping_id"] =&gt; NULL
        ["min_weight"] =&gt; string(4) "0.00"
        ["max_weight"] =&gt; string(4) "5.00"
        ["shipping_method"] =&gt; string(6) "Ground"
        ["shipping_rate"] =&gt; string(4) "8.00"
      }
      [1] =&gt; object(Shipping\Model\Shipping)#385 (5) {
        ["shipping_id"] =&gt; NULL
        ["min_weight"] =&gt; string(4) "6.00"
        ["max_weight"] =&gt; string(5) "10.00"
        ["shipping_method"] =&gt; string(6) "Ground"
        ["shipping_rate"] =&gt; string(5) "12.00"
      }
    }
    ["Expedited"] =&gt; array(4) {
      [0] =&gt; object(Shipping\Model\Shipping)#388 (5) {
        ["shipping_id"] =&gt; NULL
        ["min_weight"] =&gt; string(4) "0.00"
        ["max_weight"] =&gt; string(4) "5.00"
        ["shipping_method"] =&gt; string(9) "Expedited"
        ["shipping_rate"] =&gt; string(5) "12.00"
      }
    }
  }
  </code></pre>
  
  <p>Every time I run <code>array_column</code> for <code>max_weight</code> I get an empty array as a result. I'm supposed to use the returned array for <code>max()</code>.
  Is there a workaround for this?</p>