Friday, June 6, 2014

PHP memory consumption with Arrays and Objects (update: HHVM, phpng June-2014)

Lessons learned:
  • PHPng is significantly faster and uses significantly less memory
  • objects need more memory than arrays (+ 5-250 percent)
  • if array values are numeric, don't save them as strings!
  • saving 1M integers takes 33M of memory with PHPng (increase by factor 8)
  • saving 1M integers as strings takes 79M of memory with PHPng (increase by factor 20)
  • using SplFixedArray can reduce memory usage by 20-100 percent
  • avoid big Arrays and Objects in PHP whenever possible
    (don't use file('big_file') or explode("\n", file_get_contents('big_file')), etc.)
  • use streams whenever possible (fopen, fsockopen, etc.)
  • use generators when available with PHP 5.5 (RFC)
  • comparing 32bit to 64bit systems, memory consumption increases by 100-230 percent

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