Curl access https and CA certificate in php (code example)

function post($url, $data=array(), $refer = "", $timeout = 30, $header = array()){
    $curlObj = curl_init();
    $ssl = stripos($url,'https://') === 0 ? true : false;
    $options = array(
        CURLOPT_URL => $url,
        CURLOPT_RETURNTRANSFER => 1,
        CURLOPT_POST => 1,
        CURLOPT_POSTFIELDS => $data,
        CURLOPT_FOLLOWLOCATION => 1,
        CURLOPT_AUTOREFERER => 1,
        CURLOPT_USERAGENT => 'Webface SelfService Form',
        CURLOPT_TIMEOUT => $timeout,
        CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_0,
        CURLOPT_IPRESOLVE => CURL_IPRESOLVE_V4,
        CURLOPT_REFERER => $refer
    );  
    if (!empty($header)) {
        $options[CURLOPT_HTTPHEADER] = $header;
    }   
    if ($refer) {
        $options[CURLOPT_REFERER] = $refer;
    }   
    if ($ssl) {
        //注意看这里就是配置CA证书
        //只信任CA颁布的证书
        $options[CURLOPT_SSL_VERIFYPEER]=true;  
        //本地CA证书,用来验证网站的证书是否是CA颁布的
        $options[CURLOPT_CAINFO]=getcwd() . '/cacert.pem';
        //验证域名是否匹配
        $options[CURLOPT_SSL_VERIFYHOST] = 2;
        /*  
        //忽略证书验证,信任任何证书
        $options[CURLOPT_SSL_VERIFYHOST] = false;
        $options[CURLOPT_SSL_VERIFYPEER] = false;
        */
    }   
    curl_setopt_array($curlObj, $options);
    $returnData = curl_exec($curlObj);
    if (curl_errno($curlObj)) {
        $returnData = curl_error($curlObj);
    }   
    curl_close($curlObj);
    return $returnData;
}
$res=post("https://www.baidu.com");
var_dump($res);