Description:
------------
As a clent fd, writefds are always available, the select function will always return immediately if the writefds is enabled. but we only care about read events in this case.

PHP_FUNCTION(curl_multi_select)
{
        zval           *z_mh;
        php_curlm      *mh;
        fd_set          readfds;
        fd_set          writefds;
        fd_set          exceptfds;
        int             maxfd;
        double          timeout = 1.0;
        struct timeval  to;

        if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "r|d", &z_mh, &timeout) == FAILURE) {
                return;
        }

        ZEND_FETCH_RESOURCE(mh, php_curlm *, &z_mh, -1, le_curl_multi_handle_name, le_curl_multi_handle);

        _make_timeval_struct(&to, timeout);                                                                                
                                                                                                                           
        FD_ZERO(&readfds);                                                                                                 
        FD_ZERO(&writefds);                                                                                                
        FD_ZERO(&exceptfds);                                                                                               
                                                                                                                           
        curl_multi_fdset(mh->multi, &readfds, &writefds, &exceptfds, &maxfd);                                              
        if (maxfd == -1) {                                                                                                 
                RETURN_LONG(-1);                                                                                           
        }                                                                                                                  
                                                                                                                           
        RETURN_LONG(select(maxfd + 1, &readfds, &writefds, &exceptfds, &to));                                              
}