X509SerialNumber in minus value

[shivamjpandya]

Hello

i have get
<X509SerialNumber>-123129878107720596389594316463028097382</X509SerialNumber>

Actual Result
<X509SerialNumber>217152488813217867073780290968740114074</X509SerialNumber>

Pl suggest how to get Actual Serial Number
Any idea why we get minus Serial Number instead of Actual Result

//my code 
$cert = file_get_contents('mycert.crt');
$data=openssl_x509_parse($cert_info["cert"],true);
$certData = openssl_x509_parse("-----BEGIN CERTIFICATE-----\n".chunk_split($X509Cert, 64, "\n")."-----END CERTIFICATE-----\n")
$certData['serialNumber']

Any One facing kind this type issues pl help

Thanks in Advance