一般性能优化

Question

I am writing a function that returns an array of values to the caller. Let's say the array is:

$arr['keyN'] = $valueN;

If any '$keyN' does not have a value; its value is entered as zero.

My question is purely from a performance point of view: Is it better to give the key a value of zero or to NOT GIVE IT ANY VALUE AT ALL and have the caller test its presence if(isset($arr[$keyN]))....then execute code?

The reason I am asking this is because giving the array key a zero value will consume main memory and testing its existence will consume CPU cycles. So would it be better to take up some memory space (with a zero value) or not assign anything to the key and have the code test for its existence?

Answer 1

I think it's better not to assign nothing, so the value will be NULL, what means that no value is stored to that variable in the "simbolic table". PHP allocates memory in a dinamic fashion, unlike in C, that you would have a memory "block", even if it's useless.

Here I give you a starting link for the reading: http://www.php.net/manual/pt_BR/internals2.variables.intro.php