On Mon, 21 Apr 2003, Vegard Munthe wrote:
> I've asked these questions a number of other places. It seems no-one
> really knows. So, even if this might not be the right list for these
> questions, I hope someone can bare with me and help answer a few
> questions, or direct me to someone or some doc that can.
>
> Questions:
>
> 1) Since there are no functions to tell the memory usage of variables and
> objects, is there a way to calculate memory usage of variables and
> objects?
No, there is none. But there will be a function to show the total memory
usage in PHP 5 : memory_get_usage().
>
> 2) When a script loads different files as includes, does it take from the
> memory_limit pool of memory?
Yes
>
> 3) When leaving a function, are variables in the function's scope
> freed? I.e. is the memory used by a function completely freed for
> the rest of the script to reuse?
It's returned for the rest of the script to reuse, BUT there will always
be an allocated pool that will not be freed.
>
> 4) Is there any way to free memory used within a script? Does for
> instance $var = ""; free the memory previously used by $var?
Only a bit, doing $var = NULL will free the string contents, but not the
variable container itself.
>
> 5) Is it not aa good idea to use objects if you plan to collect thousends
> of them in PHP? Do they for some reason take up substantially more
> memory than other variables?
They do use quite a lot more memory then arrays, it just depends a
little on how they are distributed, and which variables you see in mind
for the relacement of objects.
As a final word you might want to checkout Xdebug
(http://xdebug.derickrethans.nl) which has a trace function
(xdebug_start_trace and xdebug_dump_function_trace) to see how much
memory a script uses per function call. (You will need to compile PHP
with the --enable-memory-limit option for this to work though).
Derick
--
"my other box is your windows PC"
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Derick Rethans http://derickrethans.nl/
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