在WordPress的foreach循环中，返回当前行ID和next/prev行ID

Question

在wordpress中，我试图获取当前行的id和即将到来的行的下一个id。

示例数据库：

----------------------------- 
    | id | book | orderby | 
    ----------------------------- 
    | 3 | b |  1 | 
    ----------------------------- 
    | 1 | f |  2 | 
    ----------------------------- 
    | 2 | g |  3 | 
    ----------------------------- 

代码：

$entries = $wpdb->get_results("SELECT * FROM ".$wpdb->prefix."_books" ORDER BY orderby ASC); 
foreach ($entries as $print){ 
    $prev = //on second row this would be 3 
    $current = $print->id //on second row this would be 1 
    $next = //on second row this would be 2 
} 

我觉得没有WordPress的方式，你只会增加或减少循环数组的键。这是prolly简单的修复。

Answer 1

您可以使用类似以下内容：

<?php 

$entries = $wpdb->get_results("SELECT * FROM ".$wpdb->prefix."_books ORDER BY orderby ASC"); 
$entries = array_values($entries); //shouldn't be needed, but used just in case wordpress returns a non-incrementing key structure for whatever reason 

foreach ($entries as $k=>$v) { 
    if (isset($entries[$k - 1])) { 
     $prev = $entries[$k - 1]->id; 
    } 
    else { 
     $prev = null; 
    } 

    $current = $v->id; 

    if (isset($entries[$k + 1])) { 
     $next = $entries[$k + 1]->id; 
    } 
    else { 
     $next = null; 
    } 
} 

?>