PHP：根据ID列表从多维数组中高效提取指定记录

// ID白名单数组
$idWhitelist = ["1","2","12","43","52"];

// 多维数据数组
$multidimensionalArray = [
    ["id" => "12", "name" => "Robert", "surname" => "Plant"],
    ["id" => "43", "name" => "Jimmy", "surname" => "Page"],
    ["id" => "8", "name" => "Mary", "surname" => "Stilton"]
];

[
    ["id" => "12", "name" => "Robert", "surname" => "Plant"],
    ["id" => "43", "name" => "Jimmy", "surname" => "Page"]
]

// 错误的尝试
foreach($idWhitelist as $testId){
    // 这里的 $multidimensionalArray["id"] 尝试访问一个不存在的键
    // 因为 $multidimensionalArray 是一个索引数组，其元素是关联数组
    if(in_array($testId, $multidimensionalArray["id"])){
        // ...
    }
}

<?php

// ID白名单数组
$idWhitelist = ["1","2","12","43","52"];

// 多维数据数组
$multidimensionalArray = [
    ["id" => "12", "name" => "Robert", "surname" => "Plant"],
    ["id" => "43", "name" => "Jimmy", "surname" => "Page"],
    ["id" => "8", "name" => "Mary", "surname" => "Stilton"],
    ["id" => "12", "name" => "John", "surname" => "Doe"] // 示例：ID重复的记录
];

// 用于存储筛选后的结果
$filteredResult = [];

// 遍历ID白名单
foreach($idWhitelist as $whitelistedId) {
    // 对于白名单中的每个ID，遍历多维数组中的每条记录
    foreach($multidimensionalArray as $record) {
        // 检查记录的 'id' 是否与白名单中的ID匹配
        if($record['id'] == $whitelistedId) {
            // 如果匹配，将整个记录添加到结果数组
            $filteredResult[] = $record;
            // 优化：如果确定多维数组中的ID是唯一的，并且找到一个匹配后就不需要再检查其他记录，
            // 可以在此处添加 break; 来跳出内层循环，提高效率。
            // 但如果多维数组中可能存在相同ID的多条记录且都需要提取，则不应使用 break;
            // break;
        }
    }
}

// 打印筛选结果
echo "<pre>";
print_r($filteredResult);
echo "</pre>";

/*
预期输出：
Array
(
    [0] => Array
        (
            [id] => 12
            [name] => Robert
            [surname] => Plant
        )

    [1] => Array
        (
            [id] => 43
            [name] => Jimmy
            [surname] => Page
        )

    [2] => Array
        (
            [id] => 12
            [name] => John
            [surname] => Doe
        )
)
*/

?>

<?php

// ID白名单数组
$idWhitelist = ["1","2","12","43","52"];

// 多维数据数组
$multidimensionalArray = [
    ["id" => "12", "name" => "Robert", "surname" => "Plant"],
    ["id" => "43", "name" => "Jimmy", "surname" => "Page"],
    ["id" => "8", "name" => "Mary", "surname" => "Stilton"],
    ["id" => "12", "name" => "John", "surname" => "Doe"]
];

// 1. 将ID白名单转换为一个查找表，键为ID，值为任意（例如 true）
// 使用 array_flip 可以将值作为键，键作为值，但如果白名单ID有重复，会丢失
// 更好的方式是手动构建或确保白名单无重复，然后使用 array_flip
// 或者更安全地，使用 array_fill_keys
$idWhitelistLookup = array_fill_keys($idWhitelist, true);
// 此时 $idWhitelistLookup 大致为: ["1" => true, "2" => true, "12" => true, ...]

$filteredResultOptimized = [];

// 2. 遍历多维数组一次
foreach($multidimensionalArray as $record) {
    // 3. 使用 isset() 或 array_key_exists() 在查找表中进行 O(1) 查找
    if (isset($idWhitelistLookup[$record['id']])) {
        $filteredResultOptimized[] = $record;
    }
}

echo "<pre>";
print_r($filteredResultOptimized);
echo "</pre>";

?>