Treat an empty "persistent_id" the same as omitting this parameter #1238

There does not seem to be any value that can be used for $persistent_id in

$redis->pconnect($host, $port, $timeout, $persistent_id);

such that Phpredis re-uses a connection established by omitting this parameter:

$redis->pconnect($host, $port, $timeout);

I've tried to pass '', null, true, false and 0. All are treated differently than omitting the parameter completely, i.e. a new connection is established.

Expected behaviour

When I call the pconnect method with persistent_id = '' then Phpredis should behave the same as if I omitted this parameter (because the empty string is documented as the default value).

Actual behaviour

Phpredis treats persistent_id = '' differently than omitting this parameter.

I'm seeing this behaviour on

• OS: Linux
• Redis: 4.0.1
• PHP: 7.1.9
• phpredis: 3.1.3 and 3.1.4 RC1

Steps to reproduce, backtrace or example script

<?php
$redis1 = new \Redis();
$redis1->pconnect('127.0.0.1', 6379, 0.0);

$redis2 = new \Redis();
$redis2->pconnect('127.0.0.1', 6379, 0.0, '');

echo getmypid() . "\n";
sleep(60);

Then, in another console tab, run ss -p | grep "pid=PID" (replace PIDwith the output of the script) to check how many Redis connections the script has established. Expected value: 1. Actual value: 2.

I've checked

• There is no similar issue from other users
• Issue isn't fixed in develop branch