Is it bad for performance to extract variables from an array?

Question

Hi everyone,

I have found out about the great extract function in PHP and I think that it is really handy. However I have learn that most things that are nice in PHP also affects performance, so my question is which affect using the extract can have, seen in a performance perspective?

Is it a no-no to use for big applications to extract variables outta arrays?

Answer 1

extract shouldn't be used on untrusted data. And it isn't usually useful for trusted data (because there are likely a limited number of known array keys).

Answer 2

Working with arrays in most languages is far better because the compiler and/or interpreter can use SIMD instructions with it.

Also you might notice if some part of your code tries to call one function for each value within the array. From a performance point of view it is more efficient to call the function only once with all the values packed. The overhead of calling a function several times will scale up if the array is too long and makes harder to detect possible optimizations

Answer 3

I don't see why it should be such a big performance hit, as long as you don't extract huge arrays in big loops. But I've never found a reason to use extract either :)

Answer 4

Depends on the size of the array and the scope to which your extracting it, say you extract a huge array to the global namespace, I could see that having an effect, as you will have all that data in memory twice - I believe though it may do some fun internal stuff which PHP is known to do to limit that -

but say you did

function bob(){
extract( array( 'a' => 'woo', 'b' =>'fun', 'c' => 'array' ) );
}

its going to have no real lasting effect.

Long story short, just consider what you're doing, why your doing it, and the scope.