How can manual calculations differ from calculations within for-loops in PHP?

Manual calculations in PHP require the programmer to manually input the calculations for each operation, which can be prone to errors and time-consuming. On the other hand, calculations within for-loops can automate the process, making it more efficient and less error-prone. By utilizing for-loops, repetitive calculations can be easily performed without the need for manual input.

// Manual calculation
$sum = 0;
$numbers = [1, 2, 3, 4, 5];

foreach ($numbers as $number) {
    $sum += $number;
}

echo "Sum using manual calculation: " . $sum . "\n";

// Calculation within for-loop
$sum = 0;
$numbers = [1, 2, 3, 4, 5];

for ($i = 0; $i < count($numbers); $i++) {
    $sum += $numbers[$i];
}

echo "Sum using for-loop calculation: " . $sum . "\n";