Question

I do it like this:

$r = new Predis\Client($single_server, $options);
$retval = $r->blpop('queue:query');

But I get this error:

ERR wrong number of arguments for 'blpop' command

Whenever I do this

$r = new Predis\Client($single_server, $options);
$retval = $r->blpop('queue:query',0);

I get the error:

Error while reading line from the server

Doing it from redis-cli

redis 127.0.0.1:6379> BLPOP queue:query
(error) ERR wrong number of arguments for 'blpop' command
redis 127.0.0.1:6379> BLPOP queue:query 0
1) "queue:query"
2) "hello world"

Answer 1

Seems like a bug. The latest version doesn’t have this issue, also it apparently dropped namespaces:

<?
include_once "Predis.php";

$r = new Predis_Client();
$retval = $r->blpop('queue:query',0);
var_dump($retval);
?> 

It blocked when I accessed the page. Then, I issued LPUSH queue:query 0, went back to the page, and got this:

array(2) { [0]=> string(11) "queue:query" [1]=> string(1) "0" }

Nevertheless, I would recommend the use of phpredis, it is faster than this library, because it is compiled as a php extension. If you have the rights in your server, that’s a good pick.