XML xpath search and array looping with php, memory problem

[gakshero]

I'm dealing with large XML files (several megabytes) for which I have to make various kind of checks. However I have problem with memory and time usage which grows very quickly. I've tested it like this:\[code\]$xml = new SimpleXMLElement($string);$sum_of_elements = (double)0.0;foreach ( $xml->xpath('//Amt') as $amt ) { $sum_of_elements += (double)$amt;}\[/code\]With microtime() and memory_get_usage() -funtions I get the following results by running this code:

• 5Mb file (7480 Amt-elements):
  • execution time 0,69s
  • Memory usage grows from 10.25Mb to 29.75Mb

That's still quite ok. But then with a bit bigger file memory and time usage grow very much:

• 6Mb file (8976 Amt-elements):
  • execution time 8,53s
  • Memory usage grows from 10.25Mb to 99.25Mb

The problem seems to be in looping the result set. I've also tried for-loop instead of foreach but with no difference. Without looping the memory usage does not grow so much.Any idea where the problem could be?