DB queries or session variables?

mbaweb

The navigation for our site is in a MySql DB. In an effort to reduce calls to the DB, I have created a number of arrays and stored them as session variables. Considering that this information will need to be accessed on every page of the website, is it more efficient to do repeated DB queries for this navigation information (in addition to the queries made for regular page content), or to use large arrays as session variables? How much of a performance cost is associated with session variables (on a Unix box w/ Apache, for example) and at what point does that cost outweigh repeated DB queries?

Anon

it seems difficult to quantify this ?

if keys are registered to the session then you can extract the key from the session and do either an sql query for the information you require or you can register the information to the session and extract the information from the session

so for singular information that's static(login name) registering it to the session seems the right choice as it eliminates a query step

but for multiple information that maintains state such as a check box selections,radio button selection, text box entry on a page it is not clear whether registering all these to the session or submitting them to database would result in the fastest retrieval

ie in this example we are comparing

the retrevial of 3 peices of data from a session

with the retreval of 1 piece of key data from a session and 1 sql query which selects
3 pieces of data

have limited time at the moment,will continue to look into this

i would like to see more able php programmers giving us the benefit of their experiences on this one

paulsbooker

mbaweb

In my example, I do a MySQL query where I grab and sort all the navigation into multidimensional arrays based on level. Since this navigation is often the same for any one level, I didn't want to re-query the database for that same information. I saved the array as a session variable and avoided a database query. However, I can have a large number of session variable arrays registered, is this a bad thing?