Does the garbage collector can collect elements which belongs to a script that is under `sleep()` condition?

Question

Does the garbage collector can collect elements which belongs to a script that is under sleep() condition?

I know that the garbage collector free objects from memory if they aren't referenced (so they are considered to be no more in use).

If the answer is yes, I can free resources before the script continues, so with a higher execution time I can use less memory.

Is my reasoning true?

I'll try to be clearer:

the script is running
in the script I make 3 variables eligible for being garbage collection: $var1 = $var2 = $var3 = null; or other form to make it properly, this isn't the point
in the script I invoke sleep(100);
here is where my question applies: before the time of 100 seconds ends, does the garbage collector can run to free $var1, $var2 and $var3?

Thanks a lot.

Not entirely sure what you mean, but `sleep()` just pauses execution and so the objects are still needed. — Nigel Ren, Oct 09 '19 at 07:26
@Dharman, when a variable is set to `null` becomes eligible for the garbage collector, isn't true?I tried also unset($var1, $var2, $var3); — user2342558, Oct 09 '19 at 08:56
Why would it? What would happen to the null value then? It still has a value. — Dharman, Oct 09 '19 at 08:57
o_O i'm little confused... how can I make a variable eligible for garbage collection? In Java works as it. — user2342558, Oct 09 '19 at 08:58
Have a read of https://stackoverflow.com/questions/584960/whats-better-at-freeing-memory-with-php-unset-or-var-null — Nigel Ren, Oct 09 '19 at 09:10
@NigelRen I read the post. But why did you suggest to read it? Only for the `clear variable` purpose or related of my question? (see my edit) — user2342558, Oct 09 '19 at 09:21
The garbage collector is not timing based, so using sleep() makes no difference. — NikiC, Oct 10 '19 at 16:10
@NikiC so when exactly it runs? If it isn't timing base, I may thinks I can trigger it. — user2342558, Oct 10 '19 at 16:11
Assuming you are referring to the cycle collector: When the number of GC roots exceeds a threshold. — NikiC, Oct 10 '19 at 16:12
@NikiC Hmm..... so if I define for example 1kk new variables the GC may be triggered? — user2342558, Oct 10 '19 at 17:48

jspit · Answer 1 · 2019-10-09T11:46:01.087

1

I think the space of deleted variables is released immediately. Use memory_get_usage() to determine your required memory. This is shown by the following small test:

<?php
    echo memory_get_usage(false)." start <br>";
    $var1 = range(0,10000);  //a big array
    echo memory_get_usage(false)." create var1 <br>";
    unset($var1);  
    echo memory_get_usage(false)." unset var1 <br>";

Output:

424120 start 
952560 create var1 
424120 unset var1

edited Oct 09 '19 at 11:46

answered Oct 09 '19 at 09:40

jspit

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If a variable falls out of scope and is not used in any other place of the currently executed code anymore, then it is garbage collected automatically. You can force this early by using unset() to end variables scope early. What can the garbage collector do, if you clean up self all? – jspit Oct 09 '19 at 11:49

Does the garbage collector can collect elements which belongs to a script that is under `sleep()` condition?

1 Answers1