发送方法如下：

public function sendSms()
    {   
        $params = array ();
	
		// *** 需用户填写部分 ***
		// fixme 必填：是否启用https
		$security = false;
	
		// fixme 必填: 请参阅 https://ak-console.aliyun.com/ 取得您的AK信息
		$accessKeyId = "LTA*********uLD";
		$accessKeySecret = "mfjFi7w**********NYHGi";
	
		// fixme 必填: 短信接收号码
		$params["PhoneNumbers"] = "130000000";
	
		// fixme 必填: 短信签名，应严格按"签名名称"填写，请参考: https://dysms.console.aliyun.com/dysms.htm#/develop/sign
		$params["SignName"] = "签名名称";
	
		// fixme 必填: 短信模板Code，应严格按"模板CODE"填写, 请参考: https://dysms.console.aliyun.com/dysms.htm#/develop/template
		$params["TemplateCode"] = "SMS_198540007";
	
		// fixme 可选: 设置模板参数, 假如模板中存在变量需要替换则为必填项
		$params['TemplateParam'] = Array (
			"code" => "12345",
			
		);
		// fixme 可选: 设置发送短信流水号
		//$params['OutId'] = "12345";
	
		// fixme 可选: 上行短信扩展码, 扩展码字段控制在7位或以下，无特殊需求用户请忽略此字段
		//$params['SmsUpExtendCode'] = "1234567";
	
	
		// *** 需用户填写部分结束, 以下代码若无必要无需更改 ***
		if(!empty($params["TemplateParam"]) && is_array($params["TemplateParam"])) {
			$params["TemplateParam"] = json_encode($params["TemplateParam"], JSON_UNESCAPED_UNICODE);
		}
	
		// 初始化SignatureHelper实例用于设置参数，签名以及发送请求
		$helper = new SignatureHelper();
		
		// 此处可能会抛出异常，注意catch
		$content = $helper->request(
			$accessKeyId,
			$accessKeySecret,
			"dysmsapi.aliyuncs.com",
			array_merge($params, array(
				"RegionId" => "cn-hangzhou",
				"Action" => "SendSms",
				"Version" => "2017-05-25",
			)),
			$security
		);
		return $content;
    }

 SignatureHelper完整代码（注意你的命名空间）：

<?php
 
namespace aliyunsms;
 
/**
 * 签名助手 2017/11/19
 *
 * Class SignatureHelper
 */
class SignatureHelper {
   
  
    /**
     * 生成签名并发起请求
     *
     * @param $accessKeyId string AccessKeyId (https://ak-console.aliyun.com/)
     * @param $accessKeySecret string AccessKeySecret
     * @param $domain string API接口所在域名
     * @param $params array API具体参数
     * @param $security boolean 使用https
     * @param $method boolean 使用GET或POST方法请求，VPC仅支持POST
     * @return bool|\stdClass 返回API接口调用结果，当发生错误时返回false
     */
    public function request($accessKeyId, $accessKeySecret, $domain, $params, $security=false, $method='POST') {
        $apiParams = array_merge(array (
            "SignatureMethod" => "HMAC-SHA1",
            "SignatureNonce" => uniqid(mt_rand(0,0xffff), true),
            "SignatureVersion" => "1.0",
            "AccessKeyId" => $accessKeyId,
            "Timestamp" => gmdate("Y-m-d\TH:i:s\Z"),
            "Format" => "JSON",
        ), $params);
        ksort($apiParams);
        $sortedQueryStringTmp = "";
        foreach ($apiParams as $key => $value) {
            $sortedQueryStringTmp .= "&" . $this->encode($key) . "=" . $this->encode($value);
        }
 
        $stringToSign = "${method}&%2F&" . $this->encode(substr($sortedQueryStringTmp, 1));
 
        $sign = base64_encode(hash_hmac("sha1", $stringToSign, $accessKeySecret . "&",true));
 
        $signature = $this->encode($sign);
 
        $url = ($security ? 'https' : 'http')."://{$domain}/";
 
        try {
            $content = $this->fetchContent($url, $method, "Signature={$signature}{$sortedQueryStringTmp}");
            return json_decode($content);
        } catch( \Exception $e) {
            return false;
        }
    }
 
    private function encode($str)
    {
        $res = urlencode($str);
        $res = preg_replace("/\+/", "%20", $res);
        $res = preg_replace("/\*/", "%2A", $res);
        $res = preg_replace("/%7E/", "~", $res);
        return $res;
    }
 
    private function fetchContent($url, $method, $body) {
        $ch = curl_init();
 
        if($method == 'POST') {
            curl_setopt($ch, CURLOPT_POST, 1);//post提交方式
            curl_setopt($ch, CURLOPT_POSTFIELDS, $body);
        } else {
            $url .= '?'.$body;
        }
 
        curl_setopt($ch, CURLOPT_URL, $url);
        curl_setopt($ch, CURLOPT_TIMEOUT, 5);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
        curl_setopt($ch, CURLOPT_HTTPHEADER, array(
            "x-sdk-client" => "php/2.0.0"
        ));
 
        if(substr($url, 0,5) == 'https') {
            curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
            curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, false);
        }
 
        $rtn = curl_exec($ch);
 
        if($rtn === false) {
            // 大多由设置等原因引起，一般无法保障后续逻辑正常执行，
            // 所以这里触发的是E_USER_ERROR，会终止脚本执行，无法被try...catch捕获，需要用户排查环境、网络等故障
            trigger_error("[CURL_" . curl_errno($ch) . "]: " . curl_error($ch), E_USER_ERROR);
        }
        curl_close($ch);
 
        return $rtn;
    }
}