我真的找不到我问题的直接答案，当我几乎 99% 确定我是否正确添加了所有内容时，我无法弄清楚为什么错误会被抛回。也许一双新鲜的眼睛会有所帮助。
问题：
我正在尝试向显示已添加的所有下载的表中添加新列，但是我收到此错误并且无法找出原因。我正在尝试查看下载是否已附加到产品。
错误：
Fatal error: Call to undefined function isUsed() in /customers/b/4/a/athomestudios.net/httpd.www/admin/controller/catalog/download.php on line 178
控制器/目录/下载.php：
foreach ($results as $result) {
$data['downloads'][] = array(
'download_id' => $result['download_id'],
'name' => $result['name'],
'used' => isUsed($result['download_id']),
'date_added' => date($this->language->get('date_format_short'), strtotime($result['date_added'])),
'edit' => $this->url->link('catalog/download/edit', 'token=' . $this->session->data['token'] . '&download_id=' . $result['download_id'] . $url, 'SSL')
);
}
型号/目录/下载.php：
public function isUsed($download_id) {
$query = $this->db->query("SELECT COUNT(*) as `total` FROM " . DB_PREFIX . "product_to_download WHERE download_id = '" . (int)$download_id . "'");
return $query->row['total'];
}
视图/模板/目录/download_list.php：
<?php foreach ($downloads as $download) { ?>
<tr>
<td class="text-center"><?php if (in_array($download['download_id'], $selected)) { ?>
<input type="checkbox" name="selected[]" value="<?php echo $download['download_id']; ?>" checked="checked" />
<?php } else { ?>
<input type="checkbox" name="selected[]" value="<?php echo $download['download_id']; ?>" />
<?php } ?></td>
<td class="text-left"><?php echo $download['name']; ?></td>
<td class="text-center">
<?php
if ($download['used'] == 0) {
echo 'No';
}else{
echo 'Yes';
}
?>
</td>
<td class="text-right"><?php echo $download['date_added']; ?></td>
<td class="text-right"><a href="<?php echo $download['edit']; ?>" data-toggle="tooltip" title="<?php echo $button_edit; ?>" class="btn btn-primary"><i class="fa fa-pencil"></i></a></td>
</tr>
<?php } ?>
@Fred -ii- 表示添加数据库连接字符串。
foreach ($results as $result) {
$data['downloads'][] = array(
'download_id' => $result['download_id'],
'name' => $result['name'],
'used' => $this->model_catalog_download->isUsed($result['download_id']),
'date_added' => date($this->language->get('date_format_short'), strtotime($result['date_added'])),
'edit' => $this->url->link('catalog/download/edit', 'token=' . $this->session->data['token'] . '&download_id=' . $result['download_id'] . $url, 'SSL')
);
}