Comment by whalesalad | Hacker News Reader

Comment by whalesalad | Hacker News Reader

The code looks pretty clean. I dig the two-tab spacing as well, but perhaps that was done after the fact.

Anyhow, not sure if this makes any difference or not but i'm curious as to why true PHP constants are not used, and instead regular variables in all caps like $PARAM_INT are used. Anyone know why this might be?

I ask because one of you PHP-gurus might inform me that there are certain use-cases where a true constant is not wise.

An example below:

  param_get_slashed(array(
    'feeduser' = > $PARAM_INT, //debug: gets feed for user here
    'err' = > $PARAM_STRING, // returning from a failed entry on an orientation form
    'error' = > $PARAM_STRING, // an error can also be here because the profile photo upload code is crazy
    'ret' = > $PARAM_INT, 'success' = > $PARAM_INT, // successful profile picture upload
    'jn' = > $PARAM_INT, // joined a network for orientation
    'np' = > $PARAM_INT, // network pending (for work/address network)
    'me' = > $PARAM_STRING, // mobile error
    'mr' = > $PARAM_EXISTS, // force mobile reg view
    'mobile' = > $PARAM_EXISTS, // mobile confirmation code sent
    'jif' = > $PARAM_EXISTS, // just imported friends
    'ied' = > $PARAM_STRING, // import email domain
    'o' = > $PARAM_EXISTS, // first time orientation, passed on confirm
    'verified' = > $PARAM_EXISTS)); // verified mobile phone

They might be simple input validation filters created using the create_function() function which allowed you to create anonymous functions of sorts in PHP prior to 5.3. You can't assign an anonymous function to a constant. An alternative would have been to include a big switch statement in the param_get_slashed() function but since the same validators are used in a bunch of places it seems cleaner to use anonymous functions and have each function that uses them loop through and call each function passing the parameter named in the array key in as an argument

I think it might be because if you write something like $PARAM_INT_sometypo that variable would be undefined, and it is easy to catch. But if you are using constants PARAM_INT_typo becomes a string[1]. That way you would have to do more validation about that, too.

But without more context it's not that easy to tell.

[1]: http://us.php.net/manual/en/language.constants.syntax.php (search for "undefined constant")

I'm not a PHP-guru, but it's entirely possible that they're playing around with some background configurations that would make performance tweaks in some sections of the code difficult if they're defined variables.

I guess this is an implementation of a semi-defined variable. It should probably be noted that there may be a tiny bit of performance improvement when calling isset instead of defined when checking for variable set. I'm not sure if that's one of the considerations since it would definitely be a case of premature (and ultimately pointless) optimization anywhere else, but since it's Facebook, they may have gone that far to squeeze every bit out of it they can.

true PHP constants was a performance hit.

define()'s were expensive in PHP

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