FizzBuzz 作例：functionを使う

fizzbuzz-function.php

<?php

/**
 * @param int $start
 * @param int $end
 * @return string
 */
function fizzbuzz(int $start, int $end) {
    $output = '';
    $numbers = range($start, $end);
    foreach ($numbers as $number) {
        if ($number % 3 === 0) {
            $output .= 'Fizz';
        } elseif ($number % 5 === 0) {
            $output .= 'Buzz';
        } elseif ($number % 15 === 0) {
            $output .= 'FizzBuzz';
        } else {
            $output .= $number;
        }
        $output .= PHP_EOL;
    }
    return $output;
}

echo fizzbuzz(1, 100);