error using php curl with ssl certificate on Centos - php

Question

I am using php with curl to request some API the third-party supplies,as the API doc says,I should request the api with ssl certificate,I do.but the problem is when I run the script on my local environment(mac MAMP),the script works well,but when I deploy the script on my server(centos 6.5),the API can not response correctly,it says "error certificate",how this happen?
the code:
public function http_post_xml($data, $url){
$sslcert_path = self::DATA_PATH.'cert/apiclient_cert.pem';
$sslkey_path = self::DATA_PATH.'cert/apiclient_key.pem';
$rootca_path = self::DATA_PATH.'cert/rootca.pem';
$xml = '<xml>';
foreach($data as $k=>$v){
$xml .= "<{$k}>$v</$k>";
}
$xml .= '</xml>';
$curl = curl_init();
curl_setopt($curl, CURLOPT_URL, $url);
curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1 );
curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, TRUE);
curl_setopt($curl, CURLOPT_SSL_VERIFYHOST, 1);
curl_setopt($curl, CURLOPT_SSLCERTTYPE,'PEM');
curl_setopt($curl, CURLOPT_SSLCERT, $sslcert_path);
curl_setopt($curl, CURLOPT_SSLKEYTYPE, 'PEM');
curl_setopt($curl, CURLOPT_SSLKEY, $sslkey_path);
curl_setopt($curl, CURLOPT_CAINFO, $rootca_path);
curl_setopt($curl, CURLOPT_POST, TRUE);
curl_setopt($curl, CURLOPT_POSTFIELDS, $xml);
$response = curl_exec($curl);
$rep_xml = simplexml_load_string($response, null);
$return_code = (String)$rep_xml->return_code;
return array(
'code'=>(String)$rep_xml->return_code,
'msg'=>(String)$rep_xml->return_msg
);
}
I am sure the certificate path is correct.
sorry for my bad enlish,but please help me....