Description:
------------
Running unparsable code - which shouldn't be done, of course, but - causes a memory leak. Proper, parsable code does not cause memory leaks.

Reproduce code:
---------------
<?{
  echo "Erroneous code eval():\n";
  echo "Memory used before: " . memory_get_usage() . "\n";
  for ($i = 0; $i < 1000; $i++)
  {
    eval('$foo = 1; $bar = 2; asdf');
    echo "Loop $i, memory used: " . memory_get_usage() . "\n";
  }
  echo "Memory used after: " . memory_get_usage() . "\n";

  echo "\nProper code eval():\n";
  echo "Memory used before: " . memory_get_usage() . "\n";
  for ($i = 0; $i < 1000; $i++)
  {
    eval('$foo = 1; $bar = 2;');
    echo "Loop $i, memory used: " . memory_get_usage() . "\n";
  }
  echo "Memory used after: " . memory_get_usage() . "\n";


}?>


Expected result:
----------------
Erroneous code eval():
Memory used before: 42568
Loop 1, memory used: 42568
...
Loop 999, memory used: 42568
Memory used after: 42568

Proper code eval():
Memory used before: 42568
Loop 1, memory used: 42568
...
Loop 999, memory used: 42568
Memory used after: 42568



Actual result:
--------------
Erroneous code eval():
Memory used before: 42568
Loop 0, memory used: 49960
Loop 1, memory used: 57040
Loop 2, memory used: 64088
Loop 3, memory used: 71136
...
Loop 999, memory used: 7073088
Memory used after: 7073064

Proper code eval():
Memory used before: 7073064
Loop 0, memory used: 7073376
...
Loop 999, memory used: 7073376
Memory used after: 7073352