問題描述
PHP/DOMDocument: unset() 不釋放資源 (PHP/DOMDocument: unset() does not release resources)
I've got a variable $dom that contains an instance of PHP's DOMDocument. This variable is being set and unset within a loop.
unset($dom) will not release memory, though: memory_get_usage(false) reports that only 700B of about 10MB got released. memory_get_usage(true) reports the exact same amount of memory usage before and after unset().
I tried the following:
I checked that the reference count of $dom is exactly one immediately before the call to
unset():xdebug_debug_zval('dom')reports: dom: (refcount=1, is_ref=0)=class DOMDocument { }.I tried the solution proposed in DOMDocument PHP Memory Leak but this was to no avail.
I tried
gc_enable()+gc_collect_cycles(). But this did not help either.I tried calling
$dom‑>__destruct()beforeunset()but this will result in an error as DOMDocument apparently does not have a destructor.I recursively removed all nodes in the DOM before I unset the variable. It did not make the least difference.
I tried setting the variable to null before re‑using it:
$dom = null
Now I'm out of ideas... Anybody got a suggestion what else I could try to debug or solve this problem?
Edit:
php ‑v reports 5.3.10‑1ubuntu3.2 with Suhosin‑Patch (cli)
The source code can be seen here: https://github.com/jerico‑dev/ojs/blob/dev/plugins/generic/lucene/classes/SolrWebService.inc.php#L256
The output of the first few iterations is:
before object creation: 19292296 after object creation: 29849832 before unset: 30055232 after unset: 30054448 before object creation: 29849592 after object creation: 39858840 before unset: 40079920 after unset: 40079136 before object creation: 39858272 after object creation: 49923216 before unset: 50136448 after unset: 50135664
‑‑‑‑‑
參考解法
方法 1:
This should release the memory store in $dom.
$dom = null;
(by jerico、Matthew Blancarte)