public with sharing class AS_httpSyncToWordpress {


    @future (callout=true)
    public static void sendAPIRequestInsert(Set<Id> setAllId) {
        Contact[] allContact= [Select Id,FirstName,LastName,Email FROM Contact where ID IN :setAllId];

        HttpRequest req = new HttpRequest();
        HttpResponse res = new HttpResponse();
        Http http = new Http();

        String username = 'sampleusername';
        String password = 'samplepassword';

        Blob headerValue = Blob.valueOf(username + ':' + password);
        String authorizationHeader = 'BASIC ' +
        EncodingUtil.base64Encode(headerValue);
        req.setHeader('Authorization', authorizationHeader);

        // below is just a sample endpoint
        req.setEndpoint('https://mysampleEndpoint.com:8080/wp-json/myApi/v1/create_contact');
        req.setMethod('POST');
    //    req.setHeader('Content-Length','2004');
        req.setHeader('Content-Type', 'application/json');
        req.setBody(JSON.serialize(allContact));
    //    req.setCompressed(true); // otherwise we hit a limit of 32000
        System.debug('allContact : ' + allContact);
        System.debug('REQUEST : ' + req);
        try {
            res = http.send(req);
            System.debug('RESPONSE wew ' + res.getBody());
        } catch(System.CalloutException e) {
            System.debug('Callout error: '+ e);
            System.debug(res.toString());
        }

    }
}

System.HttpRequest retrying request in response to handshake failure: sun.security.validator.ValidatorException: PKIX path validation failed: java.security.cert.CertPathValidatorException: timestamp check failed