Benford's law in php

BenfordAnalyzer.php

<?php

class BenfordAnalyzer
{
    protected array $data;

    public function __construct(array $data)
    {
        $this->data = array_filter($data, function ($value) {
            return is_numeric($value) && $value != 0;
        });
    }

    protected function getFirstDigit($number): ?int
    {
        $number = ltrim((string) abs($number), '0.');
        return $number !== '' ? (int) $number[0] : null;
    }

    public function actualDistribution(): array
    {
        $counts = array_fill(1, 9, 0);

        foreach ($this->data as $value) {
            $digit = $this->getFirstDigit($value);
            if ($digit >= 1 && $digit <= 9) {
                $counts[$digit]++;
            }
        }

        $total = array_sum($counts);
        $distribution = [];

        foreach ($counts as $digit => $count) {
            $distribution[$digit] = $total > 0 ? $count / $total : 0;
        }

        return $distribution;
    }

    public function benfordDistribution(): array
    {
        $distribution = [];
        for ($d = 1; $d <= 9; $d++) {
            $distribution[$d] = log10(1 + 1 / $d);
        }
        return $distribution;
    }

    public function compareDistributions(): array
    {
        $actual = $this->actualDistribution();
        $expected = $this->benfordDistribution();

        $comparison = [];
        foreach ($expected as $digit => $expectedProb) {
            $actualProb = $actual[$digit];
            $comparison[$digit] = [
                'digit' => $digit,
                'expected' => round($expectedProb * 100, 2),
                'actual' => round($actualProb * 100, 2),
                'difference' => round(($actualProb - $expectedProb) * 100, 2),
            ];
        }

        return $comparison;
    }

    public function deviationScore(): float
    {
        $comparison = $this->compareDistributions();
        $sum = 0;
        foreach ($comparison as $c) {
            $sum += abs($c['difference']);
        }
        return round($sum / 9, 2);
    }

    public function summaryTable(): string
    {
        $comparison = $this->compareDistributions();
        $lines = [];
        $lines[] = str_pad('رقم', 6) . str_pad('انتظار (%)', 15) . str_pad('واقعی (%)', 15) . 'اختلاف';
        $lines[] = str_repeat('-', 45);

        foreach ($comparison as $c) {
            $lines[] =
                str_pad($c['digit'], 6) .
                str_pad($c['expected'], 15) .
                str_pad($c['actual'], 15) .
                $c['difference'];
        }

        $lines[] = str_repeat('-', 45);
        $lines[] = 'شاخص انحراف: ' . $this->deviationScore() . '%';

        return implode(PHP_EOL, $lines);
    }

    /**
     * خروجی تحلیل به صورت JSON
     */
    public function toJson(): string
    {
        $comparison = $this->compareDistributions();

        $result = [
            'distribution' => $comparison,
            'deviation_score' => $this->deviationScore(),
        ];

        return json_encode($result, JSON_PRETTY_PRINT | JSON_UNESCAPED_UNICODE);
    }
}

How to Use ?

see online :

https://onlinephp.io/c/956b24

$data = [123, 154, 1780, 2950, 312, 45, 51, 68, 97, 1200, 18000, 1340000];

$analyzer = new BenfordAnalyzer($data);

echo $analyzer->toJson();