// Created on savesnippets.com · https://savesnippets.com/LLyFJvjG1g4dmD
<?php
function compoundInterest(
    float $principal,
    float $annualRate,
    int   $years,
    int   $timesPerYear = 12
): array {
    $final = $principal * (1 + $annualRate / $timesPerYear) ** ($timesPerYear * $years);
    return [
        'final'    => round($final, 2),
        'interest' => round($final - $principal, 2),
    ];
}

print_r(compoundInterest(10_000, 0.07, 10));
// [ final => 20096.61, interest => 10096.61 ]   ←  $10k at 7% APR for 10 years, monthly