Perhaps you are confusing perl with PHP. In PHP, you should always quote your hash keys, otherwise warnings are generated. Warnings of this type aren't enabled by default on PHP, so a lot of people don't realize that you can't say something like $hash[key] legally. It works, but if you benchmark it, it's something like 50% slower, simply because of all the warnings that are generated and silently discarded. To see these warnings in PHP, use the error_reporting function like: error_reporting(E_ALL);