在foreach中获取以前的数组值

$array = [1, 2, 3, 4, 5];
$previousValue = null;

foreach ($array as &$value) {
    if ($previousValue !== null) {
        echo "Previous value: " . $previousValue . "\n";
    }
    echo "Current value: " . $value . "\n";
    $previousValue = $value;
}

// 输出结果：
// Current value: 1
// Previous value: 1
// Current value: 2
// Previous value: 2
// Current value: 3
// Previous value: 3
// Current value: 4
// Previous value: 4
// Current value: 5
// Previous value: 5