如何修复PHP数组赋值时的Illegal offset type错误？

尝试在两个数组中根据post_id匹配，将对应post的标题赋值到目标数组，但出现错误：
致命错误：未捕获的TypeError: Illegal offset type，错误行位于$array[$week][$days][$day]['post_title'] = $post_data['post_title'];

错误原因 #

• $week和$days是数组对象，而非数组键名，PHP不允许用数组作为数组索引，这是报错核心。
• 原代码中$array是JSON字符串，未转换为PHP数组，is_array($array)返回false，函数直接返回false。
• $posts定义存在语法错误，缺少闭合括号。
• 多层嵌套循环效率低下，每次匹配都需遍历全部posts。

解决方案 #

1. 修正语法与格式错误：补全$posts的闭合括号，将JSON格式的$array转换为PHP数组。
2. 循环时保留键名：遍历数组时同时获取键名和值，使用键名操作数组索引。
3. 优化匹配逻辑：将$posts转换为以post_id为键的关联数组，直接通过键名匹配，避免冗余循环。

修正后的完整代码 #

<?php
// 修正语法错误，规范数组写法
$posts = [
    ['post_id' => 3, 'post_title' => 'Task 1']
];

// 将JSON字符串转为PHP关联数组
$jsonArray = '[{"week1":{"day1":[{"post_id":"3","post_type":"timebased","post_reps":"","post_sets":"","post_time":"60","post_rest":"30"},{"post_id":"2","post_type":"repsbased","post_reps":"12","post_sets":"4","post_time":"","post_rest":"35"}],"day2":[{"post_id":"1","post_type":"repsbased","post_reps":"8","post_sets":"4","post_time":"","post_rest":"30"},{"post_id":"2","post_type":"repsbased","post_reps":"8","post_sets":"5","post_time":"","post_rest":"60"}],"day3":[],"day4":[],"day5":[],"day6":[],"day7":[]}}]';
$array = json_decode($jsonArray, true);

function getTitle($array, $posts) {
    if (!is_array($array)) {
        return false;
    }

    // 构建post_id到post_title的映射，提升匹配效率
    $postMap = [];
    foreach ($posts as $post) {
        $postMap[(string)$post['post_id']] = $post['post_title'];
    }

    // 遍历周数据，保留键名
    foreach ($array as $weekKey => $week) {
        // 遍历天数据，保留键名
        foreach ($week as $dayKey => $dayPosts) {
            // 遍历当天的所有帖子
            foreach ($dayPosts as $index => $postData) {
                $postId = $postData['post_id'];
                // 存在对应标题则赋值
                if (isset($postMap[$postId])) {
                    $array[$weekKey][$dayKey][$index]['post_title'] = $postMap[$postId];
                }
            }
        }
    }

    return $array;
}

// 调用函数并输出结果
$result = getTitle($array, $posts);
print_r($result);
?>

关键修改说明 #

• 规范$posts的数组写法，修复语法错误。
• 使用json_decode($jsonArray, true)将JSON字符串转为可操作的PHP关联数组。
• 构建$postMap映射表，将匹配操作的时间复杂度从O(n*m)优化为O(n)。
• 循环时使用$weekKey、$dayKey、$index作为数组索引，避免用数组对象作为索引的错误。

内容的提问来源于stack exchange，提问作者bdroid