php - 如何从多维数组中获取此值

Question

$resolutions = array(
    '4:3' => array(
        '1024x768',
        '1600x1200',
        '2048x1536'
    ),
    '16:9' => array(
        '1280x720',
        '1366x768',
        '1600x900',
        '1920x1080',
        '2560x1440'
    ),
    '16:10' => array(
        '1280x800',
        '1440x900',
        '1680x1050',
        '1920x1200',
        '2560x1600'
    )
);

How to get 'aspect ratio', ie values: 4:3, 16:9, 16:10?

echo $resolutions[0]

doesn't output anything

Answer 1

$keys = array_keys($resolutions);
echo $keys[0];