PHP:获取数组的下一个/前一个元素，循环if last/first - PHP: Get next/prev element of an array with loop if last/first

PHP: Get next/prev element of an array with loop if last/first

我没有设法在我的投资组合中添加导航箭头。我想获得下一个和上一个id基于当前id。问题是当$current_id是数组的最后一个，我不知道如何去到第一个创建一种循环。同样的，如果$current_id是第一个元素，怎么让最后一个元素是优先的呢?我被卡住了，你能帮帮我吗?

下面是我的代码:

<?php 
    $current_id = "10";
    $array = array(
        "1" => "aa",
        "2" => "bb",
        "3" => "cc",
        "4" => "dd",
        "5" => "ee",
        "6" => "ff",
        "7" => "gg",
        "8" => "hh",
        "9" => "ii",
        "10" => "jj",
    );

    $current_index = array_search($current_id, $array);
    $next = $current_index + 1;
    $prev = $current_index - 1;
?>

对于下一个值，您可以使用模数%:

$number_of_elements = count($array);
$next = ($current_index + 1) % $number_of_elements;

和前一个if值，因为模不喜欢负数

$prev = $current_index - 1
if ($prev < 0){
    $prev = $number_of_elements - 1;
}

这样使用模:

$current_id = 9;
$array = array(
    "aa",
    "bb",
    "cc",
    "dd",
    "ee",
    "ff",
    "gg",
    "hh",
    "ii",
     "jj",
);
$next = ($current_id+($count=count($array))+1)%$count;
$previous = ($current_id+$count-1)%$count;
print("$previous $next");

您可以使用reset()和end()函数将数组指针移动到数组的开始和结束。因此，在处理数组之前你可以这样做:

end($array);
$end = key($array);

然后:

reset ($array);
while (current ($array)) {
    $current_index = key($array);
    $current_value = current($array);
    if ($current_index == $end) 
        reset($array);
    else
        next($array);
}

或者，构建某种链表，其中数组的每个元素都有指向下一个元素的指针/引用。

你可以做到，如果你有最后一个页面的id。

Try something as

$last=count($array);
$next = $current_index + 1;
$next=$next<0?$last:$next;
$prev = $current_index - 1;
$prev =$prev==$last?1:$prev