PHP XML转CSV：如何将负数库存值转换为0？

我写了一段PHP代码，用SimpleXML读取stock.xml并转换为CSV文件，但XML中的INVENTORY字段存在负数，希望将这类负数转换为0，尝试了一段判断代码但未成功，请求帮助修改代码实现需求。

原代码 #

<?php 
function readRowsFromSimpleXML(
  SimpleXMLElement $element, string $rowExpression, array $columnExpressions
): Generator {
    foreach ($element->xpath($rowExpression) as $rowNode) {
        $row = [];
        foreach ($columnExpressions as $column => $options) {
            if (is_array($options)) {
                [$expression, $callback] = $options;
            } else {
                $expression = $options;
                $callback = null;
            }
            $values = $rowNode->xpath($expression);
            if ($callback) {
                $row[$column] = $callback($values);
            } else {
                $row[$column] = (string)($rowNode->xpath($expression)[0] ?? '');
            }
        }
        yield $row;
    }
}

$rows = readRowsFromSimpleXML(
  simplexml_load_file('stock.xml'), 
  '//Item',
  $columns = [
      'ITEMNUMBER' => './ITEMNUMBER',
      'ITEMNAME' => './ITEMNAME',
      'COLOR' => './COLOR',
      'SIZE' => './SIZE',
      'BRAND' => './BRAND',
      'INVENTORY' => './INVENTORY',
      'SALESPRICE' => './SALESPRICE',
      'BARCODE' => './BARCODE'
  ]
);


$fh = fopen('stm.csv', 'w');
fputcsv($fh, array_keys($columns));
foreach ($rows as $row) {
    fputcsv($fh, array_values($row));
}
echo ('Export has been finished...');
 ?>

尝试的未成功代码片段 #

if ($columns[6]<0)
    $columns[6] .= 0 ';'; 
else 
    $columns[6] .= trim($columns[6]) . ','; 

解决方案 #

你的现有代码已经支持回调函数处理字段值，直接利用这个特性就能实现需求，无需改动核心逻辑：

1. 将$columns数组中INVENTORY的配置从字符串改为数组，第二个元素设为处理数值的回调函数
2. 在回调函数中取出XML节点的数值，判断若小于0则返回0，否则返回原数值

修改后的完整代码 #

<?php 
function readRowsFromSimpleXML(
  SimpleXMLElement $element, string $rowExpression, array $columnExpressions
): Generator {
    foreach ($element->xpath($rowExpression) as $rowNode) {
        $row = [];
        foreach ($columnExpressions as $column => $options) {
            if (is_array($options)) {
                [$expression, $callback] = $options;
            } else {
                $expression = $options;
                $callback = null;
            }
            $values = $rowNode->xpath($expression);
            if ($callback) {
                $row[$column] = $callback($values);
            } else {
                $row[$column] = (string)($rowNode->xpath($expression)[0] ?? '');
            }
        }
        yield $row;
    }
}

$rows = readRowsFromSimpleXML(
  simplexml_load_file('stock.xml'), 
  '//Item',
  $columns = [
      'ITEMNUMBER' => './ITEMNUMBER',
      'ITEMNAME' => './ITEMNAME',
      'COLOR' => './COLOR',
      'SIZE' => './SIZE',
      'BRAND' => './BRAND',
      'INVENTORY' => [
          './INVENTORY',
          function($values) {
              $value = (float)($values[0] ?? 0);
              return $value < 0 ? 0 : $value;
          }
      ],
      'SALESPRICE' => './SALESPRICE',
      'BARCODE' => './BARCODE'
  ]
);


$fh = fopen('stm.csv', 'w');
fputcsv($fh, array_keys($columns));
foreach ($rows as $row) {
    fputcsv($fh, array_values($row));
}
echo ('Export has been finished...');
 ?>

关键说明 #

• 回调函数接收xpath查询返回的$values数组，将第一个值转为浮点型（为空时默认0）
• 通过三元运算符判断数值是否小于0，实现负数转0的逻辑
• 这种方式完全适配现有代码架构，后续其他字段需要特殊处理时，也可以用同样的方式添加回调

内容的提问来源于stack exchange，提问作者Dominik Naczk