Page not available when using SplFixedArray - php

Question

I'm getting "Page not available" if I run the following code:
namespace Database;
class Table extends \Database\Connection {
// ...
/**
* Execute query and return result
* #param type $query
* #param type $sqlWildcards
* #return SplFixedArray ResultSet
*/
public static function query($query, $sqlWildcards = array()) {
// Do some query stuff
// $stmt is a PHP PDO Statement
// Additional result manipulation
$rowCount = 0;
$rsStorage = new \SplFixedArray(500000);
while ($row = $stmt->fetch(\PDO::FETCH_ASSOC)) {
$modRow = static::modifyRow($row);
if ($modRow !== false) {
$rsStorage[$rowCount] = $modRow;
$rowCount++;
}
}
// Resize
$rsStorage->setSize($rowCount);
}
}
Method modifyRow($row):
/**
* Gives the possibility to modify a result for child classes
* #param array $row
* #return array
*/
protected static function modifyRow($row) {
return $row;
}
But if I do the following:
while ($row = $stmt->fetch(\PDO::FETCH_ASSOC)) {
//$modRow = static::modifyRow($row);
//if ($modRow !== false) {
$rsStorage[$rowCount] = $modRow;
$rowCount++;
//}
}
Everything works fine!
Edit: The test above makes no sense, I forgot to set $modRow to $row - this fails as well.
Another hint: if I do something like this
while ($row = $stmt->fetch(\PDO::FETCH_ASSOC)) {
$modRow = static::modifyRow($row);
if ($modRow !== false) {
$rsStorage[$rowCount] = $modRow;
$rowCount++;
}
// Works
if($rowCount == 5000) { break; }
// Crashes (Page not available
if($rowCount == 10000) { break; }
}
Error reporting is activated but there's no internal server error, though. Just "page not available"
Edit: 9742 is the magic number. When $rowCount hits 9743 it crashes - doesn't matter if I test it from 0 to 9743 or 9744 to x
Edit2: If I use array instead of SplFixedArray everything's fine. Does not make sense since splfixedarray is more memory efficient than array()
Edit3: I wrote the memory usage into a file until the script crashes, it reaches a peak of 54MB - server limit is 128MB
Edit4: Apache log shows me a 'zend_mm_heap corrupted'
Never had this before, also google could not help me
Any idea?