从总金额反推成本、税费与佣金的PHP实现教程

<?php

/**
 * 从总金额中计算成本价、佣金和税费
 *
 * @param float $totalAmount   总金额 (销售价格)
 * @param float $commissionRate 佣金率 (例如 0.10 代表 10%)
 * @param float $taxRate       税率 (例如 0.18 代表 18%)
 * @return array               包含 'costPrice', 'commissionAmount', 'taxAmount' 的关联数组
 * @throws InvalidArgumentException 如果任何参数为负数
 */
function calculateComponentsFromTotal(float $totalAmount, float $commissionRate, float $taxRate): array
{
    // 参数校验
    if ($totalAmount < 0 || $commissionRate < 0 || $taxRate < 0) {
        throw new InvalidArgumentException("所有金额和费率必须为非负数。");
    }

    // 计算总乘数
    $multiplier = 1 + $commissionRate + $taxRate;

    // 避免除以零
    if ($multiplier === 0.0) {
        // 如果总乘数为0，则无法计算成本价，这通常意味着费率异常
        throw new InvalidArgumentException("佣金率和税率之和不能为 -1。");
    }

    // 计算成本价
    $costPrice = $totalAmount / $multiplier;

    // 计算佣金金额
    $commissionAmount = $costPrice * $commissionRate;

    // 计算税费金额
    $taxAmount = $costPrice * $taxRate;

    return [
        'costPrice'        => $costPrice,
        'commissionAmount' => $commissionAmount,
        'taxAmount'        => $taxAmount,
    ];
}

// 示例用法
$sellingPrice = 1000.00; // 总金额
$taxPercent = 0.18;      // 18% 税率
$commPercent = 0.10;     // 10% 佣金率

try {
    $results = calculateComponentsFromTotal($sellingPrice, $commPercent, $taxPercent);

    echo "原始销售价格: " . number_format($sellingPrice, 2) . "元\n";
    echo "------------------------------------\n";
    echo "计算出的成本价: " . number_format($results['costPrice'], 2) . "元\n";
    echo "计算出的佣金: " . number_format($results['commissionAmount'], 2) . "元\n";
    echo "计算出的税费: " . number_format($results['taxAmount'], 2) . "元\n";
    echo "------------------------------------\n";
    echo "各项之和 (验证): " . number_format($results['costPrice'] + $results['commissionAmount'] + $results['taxAmount'], 2) . "元\n";

} catch (InvalidArgumentException $e) {
    echo "错误: " . $e->getMessage() . "\n";
}

// 另一个例子：如果佣金率和税率都是0
echo "\n--- 另一个例子 (无佣金无税费) ---\n";
try {
    $resultsNoFees = calculateComponentsFromTotal(500.00, 0.0, 0.0);
    echo "原始销售价格: " . number_format(500.00, 2) . "元\n";
    echo "计算出的成本价: " . number_format($resultsNoFees['costPrice'], 2) . "元\n"; // 应该等于500
    echo "计算出的佣金: " . number_format($resultsNoFees['commissionAmount'], 2) . "元\n"; // 应该等于0
    echo "计算出的税费: " . number_format($resultsNoFees['taxAmount'], 2) . "元\n"; // 应该等于0
} catch (InvalidArgumentException $e) {
    echo "错误: " . $e->getMessage() . "\n";
}

?>