multivariate testing with php and google analytics

gistfile1.php

<?php
      switch(rand(1,4)) {
          case 1: $callb = array("call_button2.png", "Click to Call Button a1", "We're Here To Help"); break;
          case 2: $callb = array("call_button3.png", "Click to Call Button a2", "Our scheduling department is happy to assist you");break;
          case 3: $callb = array("call_button2.png", "Click to Call Button a3", "Our scheduling department is happy to assist you"); break;
          case 4: $callb = array("call_button3.png", "Click to Call Button a4", "We're Here To Help");break;
     }
?>

<a href="tel:<?php echo $id['PHONE']?>" onclick="_gaq.push(['_trackEvent', 'Mobile', '<?php echo $callb[1];?>', '<?php echo $callb[2];?>'])"><?php echo $id['PHONE']?></a>