AB(CD) Algorithm testing Wordpress

<?php
    function abtest($name, $A , $B , $C = false , $D = false ) {
        session_start();

        $array_options = array();
        $array_options['A']= $A;
        $array_options['B']= $B;
        if($C != false) {
            $array_options['C']= $C;
        }
        if($D != false) {
            $array_options['D']= $D;
        }
        if (isset($_SERVER['HTTP_USER_AGENT']) && preg_match('/bot|crawl|slurp|spider/i', $_SERVER['HTTP_USER_AGENT'])) {
            return $array_options[$A]; // if bot then don't allow data sqew - returns first value to allow rendering / page function - usage & goal data not stored. As A is often the original method testing it means the original page is served up.
        } else {
            $data = get_post_meta(1 , 'ABtest-' . $name , true);

            if(empty($data)) {
                $data = array();
                foreach($array_options as $key => $option) {
                    $data[$key]= array( 'served' => '1' , 'goals' => '1');
                }
            }

            if(mt_rand(0,99) <= 23) { //  percent of random serving. In practice found with mt_rand that around 20-25% is a good amount to help ofsetting the nature of "randomness", ensuring a decent enough mix is served up for actually testing the different options.
                $serve = array_rand($array_options);

                $_SESSION['ABtest-' . $name] = $serve;

            } else {
                $best = 0;
                foreach ($data as $key => $option) {
                    $Shown = $option['served'];
                    $Goals = $option['goals'];

                    $curr = $Goals / $Shown;
                    if($curr > $best) {
                        $serve = $key;
                        $best = $curr;
                    }
                }
            }
            $data[$serve]['served']++;

            update_post_meta(1 , 'ABtest-' . $name , $data);

            $_SESSION['ABtest-' . $name] = $serve;

            return $array_options[$serve];
        }
    }


    function abtestGoalHit($name , $value) {
        if(!empty($_SESSION['ABtest-' . $name])) {
            $Served = $_SESSION['ABtest-' . $name];
            $data = get_post_meta(1 , 'ABtest-' . $name , true);
            $data[$Served]['goals'] = $data[$Served]['goals'] + $value;
            update_post_meta(1 , 'ABtest-' . $name , $data);
        }
    }


    function resetABtest($name) {
        $metakey = 'ABtest-' . $name;

        return delete_post_meta(1, $metakey);
    }


    ########

    $orange = 'orange';
    $apple = 'apple';
    $pear = 'pear';
    $straw = 'strawberry';

    if(isset($_POST['conversion'])) {
        abtestGoalHit('fruitchoice' , 1);
    } else if(isset($_POST['conversion2'])) {
        abtestGoalHit('fruitchoice' , 2);
    } else if(isset($_POST['clear'])) {
        delete_post_meta(1 , 'ABtest-fruitchoice');
        unset($_SESSION['ABtest-fruitchoice']);
        die;
    }
    ?>

<h1>My fave fruit...</h1>

<p>I love <?php echo abtest('fruitchoice' , $orange , $apple , $pear , $straw); ?> the most</p>

<form method="post">
<input name="conversion" type="submit" value="I agree!" />
<input name="conversion2" type="submit" value="I couldn't agree more" />
<input name="clear" type="submit" value="Clear!" />
</form>

<a href="">No / Bounce</a>