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Using static variables as Cache_PHP tutorial
- WBOYOriginal
- 2016-07-20 11:05:47874browse
I guess you have all encountered the following situation
I have two tables, magazine (magazine information) and subscibe (subscription information). In the subscibe table, I have a magazine_id to match the number in the magazine table. Association
Now I want to make a list of browsing subscription information. There is a column in this list that displays the name of the magazine (the name field of the magazine table). One way is to use join to make an association between the two tables. Replace magazine_id with name, but this list is a search result, and the SQL query statement is spliced together. If join is added, the logic of splicing SQL will become a bit complicated, so it is better to simply make a select * from subscibe where ...., and then it will be simpler to query the magazine_id in the result set. This brings up another problem. I don’t want too many repeated queries in my program. For example, there are 10 pieces of data in the result set. All about the same magazine_id, I would have 9 more duplicate queries, so I decided to do this
function MagazineInfoById($magazine_id){
global $db;
static $magazine_info;
if (!isset($magazine_info[$magazine_id])){
$magazine_info[$magazine_id] = $db->getRow('select * from magazine where id = '. $magazine_id) ;
}
return $magazine_info[$magazine_id];
}
while (....){
$magazine_info = MagazineInfoById($magazine_id);
.....
}
The static variable $magazine_info in MagazineInfoById() becomes a cached thing, which in some cases can greatly reduce the query time times to avoid repeated queries