php SSL certificate problem: unable to get local issuer certificate

curl_setopt($ch,CURLOPT_SSL_VERIFYPEER,FALSE);

<?php

header("Content-type:audio/mp3; charset=utf-8");       

//put your params here
$cuid = "9619439";
$apiKey = "gSwM3lYXkKXp5dDuU6zBjHrr";
$secretKey = "ff9c651db48ac780c85eed057c593e89";

$auth_url = "https://openapi.baidu.com/oauth/2.0/token?grant_type=client_credentials&client_id=".$apiKey."&client_secret=".$secretKey;
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $auth_url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 5);
curl_setopt($ch,CURLOPT_SSL_VERIFYPEER,FALSE);
$response = curl_exec($ch);
if(curl_errno($ch))
{
    print curl_error($ch);
}
curl_close($ch);
$response = json_decode($response, true);
$token = $response[‘access_token‘];

function double ($a) {
    return urlencode(urlencode($a));
}

$url = "http://tsn.baidu.com/text2audio?tex=".double(‘123‘)."&lan=".double(‘zh‘)."&cuid=".double($cuid)."&ctp=".double(‘1‘)."&tok=".double($token);

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 30);
curl_setopt($ch, CURLOPT_TIMEOUT, 30);
curl_setopt($ch,CURLOPT_SSL_VERIFYPEER,FALSE);
$response = curl_exec($ch);
if(curl_errno($ch))
{
    print curl_error($ch);
}
curl_close($ch);
echo $response;
$response = json_decode($response, true);
var_dump($response);

?>