title: in_array() and multidimensional array
body: <p>I use <code>in_array()</code> to check whether a value exists in an array like below,</p>
  
  <pre><code>$a = array("Mac", "NT", "Irix", "Linux");
  if (in_array("Irix", $a)) 
  {
      echo "Got Irix";
  }
  
  //print_r($a);
  </code></pre>
  
  <p>but what about an multidimensional array (below) - how can I check that value whether it exists in the multi-array?</p>
  
  <pre><code>$b = array(array("Mac", "NT"), array("Irix", "Linux"));
  
  print_r($b);
  </code></pre>
  
  <p>or I shouldn't be using <code>in_array()</code> when comes to the multidimensional array?</p>