PHP脚本内存泄漏直到最终溢出

Question

Keep running into a weird problem with a PHP script. The idea of the script is to grab a bunch of data from a MySQL table, process it, compare it some data from another table, and print out the results to a file in CSV format.

This script will run several hundreds of thousands of iterations to complete. Problem I have is that even with using unset() on the arrays and free() on my MySQL queries, memory continues to be used up until around iteration 350,000 or so it runs out of memory.

Without fail, every time I run the script the memory allocation as reported by memory_get_usage() stays the same until approximately ever 1050 iterations. Then it will increase by exactly 262,144 bytes. Through testing it also always increments in the exact same place in the script. In the code block below it will always increment in one of the iterations of b2a (maximum of 4 possible iterations).

//up here we get the data to run analysis/comparisons on.

echo "{$lineCounter}b:  " . memory_get_usage(TRUE) . "\n"; //27525120
if ($AttResults = $db_cx->query($ObsAttQuery)) {
   echo "{$lineCounter}b1:  " . memory_get_usage(TRUE) . "\n"; //27525120
   $attArray = array();
   echo "{$lineCounter}b2: " . memory_get_usage(TRUE) . "\n"; //27525120
   while ($attRow = $AttResults->fetch_object()) {
      echo "{$lineCounter}b2a {$attRow->attId}: " . memory_get_usage(TRUE) . "\n"; //27787264
      $attArray[$attRow->attId] = $attRow->value;
   }
echo "{$lineCounter}b3: " . memory_get_usage(TRUE) . "\n"; //27787264
$AttResults->free();
if (empty($attArray)) continue;

//down here after it is done I have an unset on the $attArray variable

Any suggestions on things to try??

Answer 1

Prior to version 5.3 php had a very stupid garbage collector: Memory Leaks With Objects in PHP 5 . With this you could not even free your memory with unset() . You have to break circular references before you unset, or simply use at least php 5.3.

Answer 2

Did you look at the data retrieved by:

$attRow = $AttResults->fetch_object()

before/around iteration 1050 ?

...and... yes, I would change the assignment in the while with one fetch before the loop and one before the end to see if the memory changes.