Doc #63842 [Com]: Infinite loop in example code

Edit report at https://bugs.php.net/bug.php?id=63842&edit=1 ID: 63842 Comment by: dean at ovts dot com dot au Reported by: dean at ovts dot com dot au Summary: Infinite loop in example code Status: Not a bug Type: Documentation Problem Package: Documentation problem PHP Version: Irrelevant Block user comment: N Private report: N New Comment: If the loop is entered and curl_multi_select then returns -1, the variables determining the loop condition remain unchanged, so curl_multi_select is simply called repeatedly until such time as it returns something other than -1. Googleguy, I don't quite understand what you were saying: Is it that eventually curl_multi_select is *GUARANTEED* to return something other than -1? *IF* that's true then there's no infinite loop. However, it's still very unclear exectly how/why this code is supposed to work. I'd like to see an explanation/clarification in the docs of the return values from curl_multi_exec and curl_multi_select, and of the $active flag. What exactly does a -1 returned from curl_multi_select imply? And (again) what would it mean if $active were true, but the return value from curl_multi_exec wasn't CURLM_OK? At the moment, without any such explanation in the docs, the example code is like an opaque magic formula for how curl_multi_exec should be used. It's difficult to trust it, when there are many "alternative versions" posted on the internet, and some on other php docs pages too! Previous Comments: ------------------------------------------------------------------------ [2013-01-16 18:31:56] googleguy@php.net *Correction to my last comment "This is not a bug, because the condition of the loop is NOT dependent upon curl_multi_select." ------------------------------------------------------------------------ [2013-01-16 18:31:05] googleguy@php.net This is not a bug, because the condition of the loop is dependent upon curl_multi_select. If the curl_multi_select returns -1 the code within the loop body is simply not executed. This still does not create an infinite loop under normal conditions because eventually if all of the curl handles timeout they are freed from the select resource handle. ------------------------------------------------------------------------ [2013-01-16 15:05:07] googleguy@php.net Related To: Bug #63936 ------------------------------------------------------------------------ [2013-01-03 15:09:09] dean at ovts dot com dot au Whoops... I meant to change all the $curlMH variables to $mh to match the previous code snippet, but I only did the first one. So '$curlMH' in the above code should actually be '$mh'. Sorry about that! ------------------------------------------------------------------------ [2013-01-03 15:05:11] dean at ovts dot com dot au That would certainly fix the inifinite loop problem. I'm not clear on why you'd need to wait 100ms (or some other arbitrary amount of time) before calling curl_multi_exec again... this just seems like bad design to me (even if the libcurl docs recommend it). How many times might you end up doing this 100ms sleep? The whole point of curl_multi_select is to sleep exactly the minimum amount, and wake up as soon as some curl operation is ready to continue. What would happen if you simply ignored the return value of curl_multi_select, and did this: while (curl_multi_exec($mh, $active) === CURLM_CALL_MULTI_PERFORM); do { curl_multi_select($curlMH); while (curl_multi_exec($curlMH, $active) === CURLM_CALL_MULTI_PERFORM); } while ($active); (Also, do we need to break if curl_multi_exec doesn't return CURLM_OK, or can we just keep going until $active is false, as I've done above? What would it mean if $active were true, but the return value wasn't CURLM_OK?) ------------------------------------------------------------------------ The remainder of the comments for this report are too long. To view the rest of the comments, please view the bug report online at https://bugs.php.net/bug.php?id=63842 -- Edit this bug report at https://bugs.php.net/bug.php?id=63842&edit=1