配列を文字列に

//状況：state
$q_cate = $dbh->query("SELECT cate_ID, cate_nam FROM org_category ORDER by cate_ID");
while($row_cate = $q_cate->fetch(PDO::FETCH_ASSOC)){
echo '
<label>
<input type="checkbox" name="cate_ID[]" value="'. $row_cate["cate_ID"] .'" />'. $row_cate["cate_nam"] .'
</label>&nbsp;';
if (($row_cate["cate_ID"] == 10)||($row_cate["cate_ID"] == 16)){echo '<br />';}
}

if (isset($_POST["state"])){
　$sct_state = $_POST["state"];
　$q_state = implode(",", $sct_state) . "\n"
}