What is a version number of your Sphinx server and 
libsphinxclient?

Sphinx server is 0.9.9 and the libsphinxclient is the one that came with the server source code under the api directory.. following is from the .h file

// $Id: sphinxclient.h 2067 2009-11-13 23:23:06Z shodan $

HTH

Unfortunately, I can't reproduce this bug, everything works 
fine with the same versions. Do you face this issue every 
query or time to time?
If it possible could you reproduce this issue on the 
different platform?
It seems this is specific bug in libsphinxclient and it's 
related with your platform.

OK I just tested on a Ubuntu 10.04 server with the same code as below:

$s = new SphinxClient;
$s->setServer('localhost',6712);
$s->setMatchMode(SPH_MATCH_ANY);
$s->setMaxQueryTime(3);
$result = $s->query('foo','getProductsByName');

var_dump($result);
var_dump($s);

produces:
bool(false)
object(SphinxClient)#1 (2) {
  ["error"]=>
  string(38) "failed to send client protocol version"
  ["warning"]=>
  string(0) ""
}

Are you sure that your searchd is running on localhost:6712?

If it's ok, please try to compile and run this code:

------------------------------------------
# test.c

#include <stdio.h>
#include <stdlib.h>

#include "sphinxclient.h"

int main ()
{
    sphinx_client *client;
    sphinx_result *res;
    sphinx_bool res_bool;
    const char *query, *index;
    
    query = "foo";
    index = "getProductsByName";

    client = sphinx_create(SPH_TRUE);
    if (!client) {
        printf("failed to create client\n");
        exit(1);
    }
    
    res_bool = sphinx_set_server(client, "localhost", 6712);
    if (!res_bool) {
        printf("failed to set server\n");
        exit(1);
    }
    
    res_bool = sphinx_set_match_mode(client, SPH_MATCH_ANY);
    if (!res_bool) {
        printf("failed to set match mode\n");
        exit(1);
    }
    
    res_bool = sphinx_set_max_query_time(client, 3);
    if (!res_bool) {
        printf("failed to set max query time\n");
        exit(1);
    }
    
    res = sphinx_query(client, query, index, NULL);
    if (!res) {
        printf("query failed: %s\n", sphinx_error(client));
        exit(1);
    } 
        
    printf("Query '%s' retrieved %d of %d matches.\n", 
        query, res->total, res->total_found);

    return 0;
}
------------------------------------------

$gcc -lsphinxclient -o test test.c
$./test

I've closed this bug. The configuration file had searchd listening on another port... 

I'm very sorry to have wasted your time on this however the error message about 'missing client protocol versions' is IMO a bit misleading...

Thanks for your help with this...

It's just a copy of error message from linsphinxclinet. I 
agree that this is a bit misleading and perhaps it makes 
sense to open related bug on sphinxsearch.com.

Thank you for your interest in PECL.