PHP布隆过滤器结合机器学习算法的实践研究

<?php
class BloomFilter {
    private $bitArray; // 位数组
    private $hashFunctions; // 哈希函数

    public function __construct($size, $hashFunctions) {
        $this->bitArray = new SplFixedArray($size);
        for ($i = 0; $i < $size; $i++) {
            $this->bitArray[$i] = false;
        }
        $this->hashFunctions = $hashFunctions;
    }

    public function add($item) {
        foreach ($this->hashFunctions as $hashFunction) {
            $index = $hashFunction($item) % count($this->bitArray);
            $this->bitArray[$index] = true;
        }
    }

    public function contains($item) {
        foreach ($this->hashFunctions as $hashFunction) {
            $index = $hashFunction($item) % count($this->bitArray);
            if (!$this->bitArray[$index]) {
                return false;
            }
        }
        return true;
    }
}

class MachineLearningBloomFilter extends BloomFilter {
    private $model; // 机器学习模型

    public function __construct($size, $hashFunctions, $model) {
        parent::__construct($size, $hashFunctions);
        $this->model = $model;
    }

    public function contains($item) {
        if ($this->model->predict($item) == 1) {
            return parent::contains($item);
        }
        return false;
    }
}

// 使用示例
$size = 1000;
$hashFunctions = [
    function($item) { return crc32($item); },
    function($item) { return (int)substr(md5($item), -8, 8); }
];
$model = new MachineLearningModel(); // 机器学习模型需要自己实现

$bloomFilter = new MachineLearningBloomFilter($size, $hashFunctions, $model);

$item = "example";
$bloomFilter->add($item);

if ($bloomFilter->contains($item)) {
    echo "Item exists!";
} else {
    echo "Item does not exist!";
}
?>