输出select的PHP递归函数

function generateSelectOptions($options, $selectedValue = null, $indent = 0) {
    foreach ($options as $value => $label) {
        $padding = str_repeat(' ', $indent * 4);
        $isSelected = ($selectedValue == $value) ? 'selected' : '';
        
        echo '<option value="' . $value . '" ' . $isSelected . '>' . $padding . $label . '</option>';
        
        if (is_array($label)) {
            generateSelectOptions($label, $selectedValue, $indent + 1);
        }
    }
}

$options = array(
    '1' => 'Option 1',
    '2' => 'Option 2',
    '3' => array(
        '3.1' => 'Option 3.1',
        '3.2' => 'Option 3.2',
        '3.3' => array(
            '3.3.1' => 'Option 3.3.1',
            '3.3.2' => 'Option 3.3.2'
        )
    )
);

generateSelectOptions($options, '3.3.1');