带有上一个和下一个元素的PHP foreach打印阵列

Question

我有一个数组$ data，我想用foreach打印它（$ data as $ detail）。事情是我想要在foreach中打印上一个和下一个元素。事情是这样的：

$data = array(1,2,3,4,5,6,7,8); 

// foreach result should look like this 
8,1,2 
1,2,3 
2,3,4 
3,4,5 
4,5,6 
5,6,7 
6,7,8 
7,8,1 

Answer 1

你可以去：

$data = array (1,2,3,4,5,6,7,8); 
$count = count ($data); 
foreach ($data as $key => $current) 
{ 
    if (($key - 1) < 0) 
    { 
    $prev = $data[$count - 1]; 
    } 
    else 
    { 
    $prev = $data[$key - 1]; 
    } 

    if (($key + 1) > ($count - 1)) 
    { 
    $next = $data[0]; 
    } 
    else 
    { 
    $next = $data[$key + 1]; 
    } 

echo $prev . ', ' . $current . ', ' . $next . "\n"; 

或者，如果简洁是一个问题：

$count = count ($data); 
foreach ($data as $i => $current) 
{ 
    $prev = $data[(($i - 1) < 0) ? ($count - 1) : ($i - 1)]; 
    $next = $data[(($i + 1) > ($count - 1)) ? 0 : ($i + 1)]; 

    echo $prev . ',' . $current . ',' . $next . "\n"; 
} 

Answer 2

<?php 

$data = array(1,2,3,4,5,6,7,8); 
$count = count($data); 

foreach($data as $index => $number) 
{ 
    $previous = $data[($count+$index-1) % $count]; // '$count+...' avoids problems 
               // with modulo on negative numbers in PHP 
    $current = $number; 
    $next = $data[($index+1) % $count]; 

    echo $previous.", ".$current.", ".$next."\n"; 
} 

关于负数模：http://mindspill.net/computing/cross-platform-notes/php/php-modulo-operator-returns-negative-numbers.html

Answer 3

相同的结果完成差异erently：

<?php 
$data = range(1,16); 
$count=count($data); 
$ret=''; 

for($i=0;$i<$count;$i++){ 
    $ret.=($i==0)?$data[$count-1].',':$data[$i-1].','; 
    $ret.=$data[$i].','; 
    $ret.=($i+1>=$count)?$data[$count-$i-1]:$data[$i+1].'<br>'; 
} 
echo $ret; 
?> 
Result: 
16,1,2 
1,2,3 
2,3,4 
3,4,5 
4,5,6 
5,6,7 
6,7,8 
7,8,9 
8,9,10 
9,10,11 
10,11,12 
11,12,13 
12,13,14 
13,14,15 
14,15,16 
15,16,1