为什么array_search在这里不起作用

我正在为前端编写一个动态的进度条脚本，结果不起作用，但我很快就要完成了。我相信这对你们中的一些人来说将是一项轻松的任务。请问这里怎么了？

// Progress Bar configurations
$data = array(
    array('bronze_V','bronze_IV','bronze_III','bronze_II','bronze_I'),
        array('silver_V','silver_IV','silver_III','silver_II','silver_I'),
        array('gold_V','gold_IV','gold_III','gold_II','gold_I'),
        array('platinum_V','platinum_IV','platinum_III','platinum_II','platinum_I'),
        array('diamond_V','diamond_IV','diamond_III','diamond_II','diamond_I')
);
foreach ($data as $key => &$value):
    $value = implode(",", $value);
endforeach;
$dataimplode = explode(",",(implode(",", $data)));
$startKey = array_search($start_rank, $dataimplode);
$currentKey = array_search($current_rank, $dataimplode);
$endKey = array_search($finish_rank, $dataimplode);
$orderPercent = (($currentKey-$startKey)/($endKey-$startKey))*100;
echo "<pre>", var_dump($dataimplode), "</pre><br/>";
echo $startKey;
echo $currentKey;
echo $endKey;