reuse of SQL query results without rerunning query and with minimal memory use

[Dave224]

I ran into a similar problem troubleshooting a modification to a plugin. I used a foreach after a query to output some variables in the query results. Subsequent plugin code used a while (!$results->EOF) loop to process the query results again, but consistently fails. I discovered that !$results->EOF was false at the while loop even though there were results from the preceding foreach loop. I tried LAT9's approach but at least EOF is not restored. Removing my troubleshooting foreach loop eliminated the problem and the while loop executed normally.

I would like to understand and avoid this problem in future troubleshooting activities. Any other suggestions on how to reset the query results including EOF?

TIA. Dave
zc157c, PHP 8.0.22, mysql 5.7.39

[dbltoe]

zc157c, PHP 8.0.22, mysql 5.7.39

While 1.5.7c should not have problems with PHP 8.0, your version of the mod may not like that version.
Have you tried dropping the PHP down a notch?

[mc12345678]

I ran into a similar problem troubleshooting a modification to a plugin. I used a foreach after a query to output some variables in the query results. Subsequent plugin code used a while (!$results->EOF) loop to process the query results again, but consistently fails. I discovered that !$results->EOF was false at the while loop even though there were results from the preceding foreach loop. I tried LAT9's approach but at least EOF is not restored. Removing my troubleshooting foreach loop eliminated the problem and the while loop executed normally.

I would like to understand and avoid this problem in future troubleshooting activities. Any other suggestions on how to reset the query results including EOF?

TIA. Dave
zc157c, PHP 8.0.22, mysql 5.7.39

Seeing that you are using a version greater than the base Zen Cart 1.5.5, there is a database method called rewind that will accomplish your desired goal.

If you did a query that resulted in the variable $results containing your query results, then calling: $results->rewind(); at a point after your usage and before the plugin's while loop, then the query results should be reset to the beginning and allow "proper" processing.

Alternatively, the plugin could be updated to also use the foreach loop, though be mindful that the internal loop may have done some other actions to the query loop that need to be considered. "Normal" code though would be to change the while to a foreach and other changes likely identified: https://docs.zen-cart.com/dev/code/d...-row-responses

Mind you that wasn't exactly easy to find, but it is an example of differences.

[mc12345678]

What I did in a plugin that still bridges Zen Cart versions was to test for the existence of the method, if it existed then do the rewind, if it didn't then use the ->Move(0) operation then do a ->MoveNext() operation.

 if (method_exists($results, 'rewind')) {
 $results->rewind();
} else {
 $results->Move(0);
 $results->MoveNext();
}

With that being any time after initially touching $results, but before the next desired access of the original $results.

[Dave224]

Thank you so much mc. $results->rewind() did the trick! Donation on the way.
Dave