"Additionally, there are certain types of circular references that may never be freed under this scheme, although that's not a huge concern to look at from the

"Additionally, there are certain types of circular references that may never be freed under this scheme, although that's not a huge concern to look at from the start." Early versions of PHP were released in the late 90s, with PHP 4, the first Zend Engine version, released in 2000. The first PHP that didn't leak cycles (PHP 5.3.0) was released in 2009. Beware of how long "not a huge concern to look at from the start" can last. http://php.net/manual/en/features.gc.collecting-cycles.php http://php.net/manual/en/features.gc.collecting-cycles.php http://php.net/ChangeLog-5.php#5.3.0 http://php.net/ChangeLog-5.php#5.3.0