PHP Sessions on MS Azure Redis service

I sure hope you’ll never end up facing this, but in case you do indeed have a PHP application on MS Azure, and you want to use MS Azure Redis service for the session backend, you’ll have to set your session.save_path to something like:

session.save_path='tcp://UNIQUENAME.redis.cache.windows.net:6379?auth=MSHATESYOU4FUNandPROFIT=&timeout=1&prefix=OHNOMS'

Easy enough, unless your auth key happens to contain a + symbol. In that case, your PHP session creation will fail with this error:

# php count.php
PHP Fatal error:  Uncaught exception 'RedisException' with message 'Failed to AUTH connection' in count.php:3
Stack trace:
#0 count.php(3): session_start()
#1 {main}
  thrown in count.php on line 3
PHP Fatal error:  Uncaught exception 'RedisException' with message 'Failed to AUTH connection' in [no active file]:0
Stack trace:
#0 {main}
  thrown in [no active file] on line 0

From redis-cli the authentication was working fine, so it took us a while to debug. It ended up being a problem with the + symbol, and the the quickest solution in our case was to just regen the auth key so it didn’t have a + in it, but I suspect (but I didn’t test this solution) that URLencoding the + as %2B might work as well.

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