在PHP中如何在循环中递归地联接字符串

$strings = ['Hello', 'World', 'from', 'PHP'];
$result = '';

foreach ($strings as $string) {
    $result .= $string . ' ';
}

echo trim($result); // 输出: Hello World from PHP

$strings = ['Hello', 'World', 'from', 'PHP'];
$result = implode(' ', $strings);

echo $result; // 输出: Hello World from PHP

$strings = ['Hello', 'World', 'from', 'PHP'];
$result = array_reduce($strings, function($carry, $item) {
    return $carry . $item . ' ';
}, '');

echo trim($result); // 输出: Hello World from PHP

class StringBuilder {
    private $str = '';

    public function append($string) {
        $this->str .= $string;
        return $this;
    }

    public function __toString() {
        return $this->str;
    }
}

$strings = ['Hello', 'World', 'from', 'PHP'];
$builder = new StringBuilder();

foreach ($strings as $string) {
    $builder->append($string)->append(' ');
}

echo trim((string)$builder); // 输出: Hello World from PHP