HTML / PHP - 表单选择框大于数据库值，在每个选择值中增加500

Question

我正在尝试创建类似于拍卖/出价表/表单的内容。 如果值（当前出价）为1000，我正在尝试创建一个允许其他用户以500为间隔出价的选择框，因此对于此示例，结果将如下：

Current Bid: 1000
Buy Now: 5000
<select class="form-control">
<option value="1500">1500</option>
<option value="2000">2000</option>
<option value="2500">2500</option>
<option value="3000">3000</option>
<option value="3500">3500</option>
<option value="4000">4000</option>
<option value="4500">4500</option>
</select>

这样的事情：

<?php
$query = $db->query('SELECT * FROM auctions WHERE available = 1 LIMIT 1');
$num = $query->num_rows;
if($num > 0) {
echo '<select class="form-control">';

foreach($query as $row) {

$currentBid = $row['currentBid']; // 1000
$buyNow = $row['buyNow']; // 5000


$bids = ?? // this is where I am stuck, how can I make the difference between $currentBid and $buyNow show as options divided by 500's


echo '
<option value="'.$bids.'">'.$bids.'</option>
';


}

echo '</select>';


}
else {
echo "No auctions available";
}

?>

Answer 1

...
$currentBid = $row['currentBid'];
$buyNow = $row['buyNow'];
...
$options = '';
for($p = $currentBid + 500; $p <= $buyNow; $p += 500) {
  $options .= '<option value="'.$p.'">'.$p.'</option>';
}