title: multidimensional array array_sum
body: <p>I have seen various posted about this question so am aware some answers to this may exist. however I am none the wiser after reading these. </p>
  
  <p>I have an array that is like the following.</p>
  
  <pre><code>[0] =&gt; Array
      (
          [id] =&gt; 95659865986
          [invoiceNumber] =&gt; 6374324
          [invoiceTitle] =&gt; Monthly
          [invoiceStatus] =&gt; Paid
          [accountId] =&gt; 6235218753
          [totalExVat] =&gt; 158.95
          [dateCreated] =&gt; 1 Apr 2012
          [vatAmount] =&gt; 20.00
      )
  </code></pre>
  
  <p>All I wish to do is do array sum on the <code>vatAmount</code> values of this array.</p>
  
  <p>As the following doesnt seem to be doing much.</p>
  
  <pre><code>(array_sum($account_invoices['vatAmount'])
  </code></pre>