add.php

<?php

// the function reads the comment added after the function is called using a backtrace and uses them as arguments
function add(): float
{
    $trace = debug_backtrace();
    $file = $trace[0]['file'];
    $line = $trace[0]['line'];

    $content = file($file);
    $lineContent = trim($content[$line - 1]);
    $ast = token_get_all("<?php\n{$lineContent}");

    $args = [];
    foreach ($ast as $token) {
        if (!is_array($token)) {
            continue;
        }
        if ($token[0] !== T_COMMENT) {
            continue;
        }

        $commentContent = $token[1];
        if (str_starts_with($commentContent, '#')) {
            $commentContent = substr($commentContent, 1);
        } else {
            $commentContent = substr($commentContent, 2);
        }
        $commentContent = trim($commentContent);
        $commentContent = preg_replace("@\s+@", " ", $commentContent);
        $args = explode(" ", $commentContent);
        $args = array_map(function (string $arg) {
            if (!is_numeric($arg)) {
                throw new InvalidArgumentException('Argument must be a number');
            }

            return str_contains($arg, '.') ? (float) $arg : (int) $arg;
        }, $args);
        break;
    }

    return array_sum($args);
}

echo add(); // 7 8 9
// the above code prints 24
echo add(); # 1 2 3
// the above code prints 6