How to use oss web direct transmission in php

<?php namespace Service;class OssUploadSignature{

    private $accessKeyId;
    private $accessKeySecret;
    private $expire = 300; // 5分钟有效期
    private $bucketHost; // Bucket 域名
    private $conditions = [ // 限制
        [
            &#39;content-length-range&#39;, // 内容限制
            0,                  // 最小上传
            10 * 1024 * 1024 // 最大上传10m
        ], [
            0 => 'starts-with',
            1 => '$key', // 必须带key
            2 => 'images/', // 如:/images  只能放在/images的路径
        ]
    ];

    public function setBucketHost($bucketHost)
    {
        $this->bucketHost = $bucketHost;
        return $this;
    }

    public function setAccessKeyId($accessKeyId)
    {
        $this->accessKeyId = $accessKeyId;
        return $this;
    }

    public function setAccessKeySecret($accessKeySecret)
    {
        $this->accessKeySecret = $accessKeySecret;
        return $this;
    }

    public function signatureConfig()
    {
        $end = time() + $this->expire;
        $arr = [
            'expiration' => $this->gmt_iso8601($end),
            'conditions' => $this->conditions,
        ];
        $base64Policy = base64_encode(
            json_encode($arr)
        );
        $signature = base64_encode(hash_hmac('sha1', $base64Policy, $this->accessKeySecret, true));
        return [
            'OSSAccessKeyId' => $this->accessKeyId,
            'policy' => $base64Policy,
            'signature' => $signature,
            'expire' => $end,
            'bucketHost' => $this->bucketHost        ];
    }


    // fix bug https://connect.console.aliyun.com/connect/detail/162632
    public function gmt_iso8601($time)
    {
        return (new \DateTime(null, new \DateTimeZone('UTC')))->setTimestamp($time)->format('Y-m-d\TH:i:s\Z');
    }}