PHP和机器学习：如何进行用户行为分析与个性化推荐

<?php
  
// 输入用户喜欢的物品列表
$user_items = array("电影1", "电影2", "音乐1", "音乐2");
  
// 所有物品的特征
$all_items = array(
    "电影1" => "喜剧",
    "电影2" => "动作",
    "电影3" => "剧情",
    "音乐1" => "流行",
    "音乐2" => "摇滚",
    "音乐3" => "古典"
);
  
// 计算相似度
$similar_items = array();
foreach ($all_items as $item => $feature) {
    $similarity = similarity($user_items, $feature);
    $similar_items[$item] = $similarity;
}
  
// 按相似度降序排序
arsort($similar_items);
  
// 推荐前n个物品
$recommend_items = array_slice($similar_items, 0, 3);
  
// 输出推荐结果
foreach ($recommend_items as $item => $similarity) {
    echo $item . " (相似度：" . $similarity . ")" . "<br>";
}
  
// 计算相似度函数
function similarity($user_items, $feature) {
    $similarity = 0;
    foreach ($user_items as $user_item) {
        if ($feature == $all_items[$user_item]) {
            $similarity++;
        }
    }
    return $similarity;
}
  
?>

<?php
  
// 用户对物品的评分矩阵
$ratings = array(
    "用户1" => array("电影1" => 5, "电影2" => 4, "音乐1" => 3),
    "用户2" => array("电影1" => 2, "电影3" => 4, "音乐2" => 5),
    "用户3" => array("音乐1" => 4, "音乐2" => 3, "音乐3" => 2)
);
  
// 计算用户之间的相似度
$user_similarity = array();
foreach ($ratings as $user1 => $items1) {
    foreach ($ratings as $user2 => $items2) {
        if ($user1 != $user2) {
            $similarity = similarity($items1, $items2);
            $user_similarity[$user1][$user2] = $similarity;
        }
    }
}
  
// 按相似度降序排序
foreach ($user_similarity as $user => $similarity) {
    arsort($similarity);
    $user_similarity[$user] = $similarity;
}
  
// 推荐前n个物品
$recommend_items = array();
foreach ($user_similarity as $user => $similarity) {
    foreach ($similarity as $similarity_user => $similarity_value) {
        foreach ($ratings[$similarity_user] as $item => $rating) {
            if (!isset($ratings[$user][$item])) {
                $recommend_items[$item] += $rating * $similarity_value;
            }
        }
    }
}
  
// 按推荐值降序排序
arsort($recommend_items);
  
// 输出推荐结果
foreach ($recommend_items as $item => $recommend_value) {
    echo $item . " (推荐值：" . $recommend_value . ")" . "<br>";
}
  
// 计算相似度函数
function similarity($items1, $items2) {
    $similarity = 0;
    foreach ($items1 as $item => $score1) {
        if (isset($items2[$item])) {
            $score2 = $items2[$item];
            $similarity += $score1 * $score2;
        }
    }
    return $similarity;
}
  
?>