Question

I have a question that I cannot find an answer.

I’m constructing a very big array that contain hex values of a file (like $array[0]=B5 $array[1]=82 and so on until $array[1230009])

When I create a function to manipulate some offsets in that array and pass the $array as reference ( function parse(&$array) { ... }) it takes WAY longer than if I pass the array normaly ( function parse($array) { ... }) ..

How is that possible ?

PS: Is there any faster way not to use array at all ? Just to use a $string = “B5 82 00 1E ..etc”, but I need to track the Offset as i advance in reading hex values as some of this values contains lengths”

Answer 1

There are some informations that might help in the following article : Do not use PHP references

Close to the end of that post, Johannes posts the following portion of code (quoting) :

function foo(&$data) {
    for ($i = 0; $i < strlen($data); $i++) {
        do_something($data{$i});
    }
}

$string = "... looooong string with lots of data .....";
foo(string);

And a part of the comment that goes with it is (still quoting) :

But now in this case the developer tried to be smart and save time by
passing a reference.
But well, strlen() expects a copy.

copy-on-write can’t be done on references so $data will be
copied for calling strlen(), strlen() will do an absolutely simple
operation – in fact strlen() is one of the most trivial functions
in PHP – and the copy will be destroyed immediately.

You might well be in a situation like this one, considering the question you are asking…