[php-src] Issue #7944: api to set memory_limit to "at least" this much

Issue: https://github.com/php/php-src/issues/7944 Comment Author: KapitanOczywisty > wonder how "unlimited" would be represented in such a function tho, should it return > -1 for no limit? or null? PHP uses int|null or int|false in similar cases. > Wouldn't it be better, if there was a way to retrieve the currently set memory limit as > _number_? This will help OP, but I wonder if there is a chance to add callback for when ini settings are changed, this would allow to control what libraries are doing and in this case control memory limit. ini_changed(string $name, callback $value); with $value = fn($old_value, $new_value)=>$new_value.   Also ini_set supposed to return false on failure, but if you try setting ridiculous value like ini_set('memory_limit', '2K') you'll get old value, and ini_get will return 2K, but limit remains unchanged - limit cannot be lower than currently allocated. [/main/main.c#L261-L283](https://github.com/php/php-src/blob/20d8561ed4986c3ca1e514b7bcb2dda8b6fbe0ee/main/main.c#L261-L283) [/Zend/zend_alloc.c#L2669-L2678](https://github.com/php/php-src/blob/20d8561ed4986c3ca1e514b7bcb2dda8b6fbe0ee/Zend/zend_alloc.c#L2669-L2678)