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PHP 計算加權平均分完整實現：從表單到結果

編輯：PHP 綜合知識

學生成績系統、綜合評價模型常需計算加權平均分。本文提供完整的三頁式實現：課程數輸入 → 成績權重錄入 → 結果展示，涵蓋 Session 狀態管理與數據驗證。

完整流程實現

步驟 1：輸入課程數量 (index.php)

<form action="step2.php" method="post">
    課程數量: <input type="number" name="course_number" min="1" max="50" required>
    <button type="submit">下一步</button>
</form>

步驟 2：錄入成績與學分 (step2.php)

<?php
session_start();
$n = (int)($_POST['course_number'] ?? 0);
if ($n < 1 || $n > 50) die('課程數量異常');
$_SESSION['course_number'] = $n;
?>

<form action="result.php" method="post">
    <?php for ($i = 0; $i < $n; $i++): ?>
        <div class="course-row">
            <label>課程 :</label>
            <input type="number" name="score[]" step="0.1" min="0" max="100" placeholder="分數" required>
            <input type="number" name="credit[]" step="0.1" min="0" max="10" placeholder="學分/權重" required>
        </div>
    <?php endfor; ?>
    <button type="submit">計算加權平均</button>
</form>

步驟 3：計算並展示結果 (result.php)

<?php
session_start();
$n = $_SESSION['course_number'] ?? 0;
$scores  = $_POST['score']  ?? [];
$credits = $_POST['credit'] ?? [];

if (count($scores) !== $n || count($credits) !== $n) {
    die('數據不完整，請重新提交');
}

$totalWeight = 0;
$weightedSum = 0;

for ($i = 0; $i < $n; $i++) {
    $score  = (float)$scores[$i];
    $credit = (float)$credits[$i];
    
    // 基礎驗證
    if ($score < 0 || $score > 100) die("第 {$i+1} 門課分數超出範圍");
    if ($credit <= 0) die("第 {$i+1} 門課學分必須大於 0");
    
    $weightedSum  += $score * $credit;
    $totalWeight  += $credit;
}

$gpa = $totalWeight > 0 ? round($weightedSum / $totalWeight, 2) : 0;
?>

<h2>計算結果</h2>
<table>
    <tr><th>課程</th><th>分數</th><th>權重</th><th>加權分</th></tr>
    <?php for ($i = 0; $i < $n; $i++): 
        $w = round($scores[$i] * $credits[$i], 2);
    ?>
    <tr>
        <td></td>
        <td></td>
        <td></td>
        <td></td>
    </tr>
    <?php endfor; ?>
    <tr class="total">
        <td colspan="2">總計</td>
        <td></td>
        <td></td>
    </tr>
</table>

<h3>加權平均分: <strong></strong></h3>
<a href="index.php">重新計算</a>

核心算法解析

function calculateWeightedAverage(array $scores, array $credits): float {
    if (count($scores) !== count($credits)) {
        throw new InvalidArgumentException('分數與權重數量不匹配');
    }
    
    $sum = 0;
    $totalWeight = 0;
    
    foreach ($scores as $i => $score) {
        $weight = $credits[$i];
        if ($weight <= 0) continue; // 或拋出異常
        $sum += $score * $weight;
        $totalWeight += $weight;
    }
    
    return $totalWeight > 0 ? $sum / $totalWeight : 0;
}

進階功能擴展

1. 等級制換算 (GPA 4.0 模式)

function scoreToGradePoint(float $score): float {
    if ($score >= 90) return 4.0;
    if ($score >= 85) return 3.7;
    if ($score >= 82) return 3.3;
    if ($score >= 78) return 3.0;
    if ($score >= 75) return 2.7;
    if ($score >= 72) return 2.3;
    if ($score >= 68) return 2.0;
    if ($score >= 64) return 1.5;
    if ($score >= 60) return 1.0;
    return 0.0;
}

2. 學期/年度統計

class GPACalculator {
    private array $courses = [];
    
    public function addCourse(string $name, float $score, float $credit, string $semester): self {
        $this->courses[] = compact('name', 'score', 'credit', 'semester');
        return $this;
    }
    
    public function getGPA(?string $semester = null): float {
        $filtered = $semester 
            ? array_filter($this->courses, fn($c) => $c['semester'] === $semester)
            : $this->courses;
        return calculateWeightedAverage(
            array_column($filtered, 'score'),
            array_column($filtered, 'credit')
        );
    }
    
    public function getReport(): array {
        $semesters = array_unique(array_column($this->courses, 'semester'));
        return array_map(fn($s) => [
            'semester' => $s,
            'gpa' => $this->getGPA($s),
            'credits' => array_sum(array_filter($this->courses, fn($c) => $c['semester'] === $s))
        ], $semesters);
    }
}