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POWhy does a simple PHP unset() memory test utilize twice the amount of memory in PHP 5.3?
 

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  1. POWhy does a simple PHP unset() memory test utilize twice the amount of memory in PHP 5.3?
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    <p>I was testing out whether unset() affects memory while the script is running, to see if unset() or other known method, $var=null is more efficient. unset() did affect memory, but since I tested it out on two different virtualhosts, I wondered why does one take more or less twice the amount of memory for the same script? I'm guessing the answer is something simple, but it escapes me at the moment. Script itself is below:</p> <pre><code>&lt;?php $init=memory_get_usage(); $test=array(); for($i=0;$i&lt;=100000;$i++){ $test[$i]=rand(0,10000000); } echo 'MEMORY CHANGE: '.((memory_get_usage()-$init)/1024/1024).'MB&lt;br/&gt;'; for($i=0;$i&lt;=100000;$i++){ unset($test[$i]); } echo 'MEMORY CHANGE: '.((memory_get_usage()-$init)/1024/1024).'MB&lt;br/&gt;'; //output on PHP 3.2.5 virtualhost: //MEMORY CHANGE: 6.98558807373MB //MEMORY CHANGE: 0.500259399414MB //output on PHP 5.3.5 virtualhost //MEMORY CHANGE: 13.970664978MB //MEMORY CHANGE: 1.00063323975MB ?&gt; </code></pre> <p>Thanks!</p>
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    1. COShouldn't you reset `$init` in between the loops?
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      1. USRichard Marskell - Drackir
    2. COAnd if you use memory_get_usage(true) rather than memory_get_usage()?
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      1. USMark Baker
    3. COSame thing happens. 3.2.5: MEMORY CHANGE: 7.25MB MEMORY CHANGE: 1MB 3.3.5: MEMORY CHANGE: 14.25MB MEMORY CHANGE: 1.75MB There must be something about the server, but I don't know what to look for.
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