PHP function for auto increment with changed value

Question

I have a requirement where I need to insert user_id in following format

13310_userid_1
13310_userid_2
13310_userid_3

where

13310 = $_GET['userid'] //user id from session
userid = constant //constant text defined
1/2/3 = autoincrement value

Here the variation is when user_id is changed, the auto increment value will be inserted from beginning which would look like

13311_userid_1
13311_userid_2
13311_userid_2

and not

13311_userid_4
13311_userid_5
13311_userid_6

How can I check if the user_id is changed and insert auto increment value from 1 ?

Thanks

Answer 1

I'm not sure it's that you need, but you can use an array to store increment of each cont :

$const = 'userid';
$user_id = '13310';
$array_increment[$user_id] =1;
foreach(array('Franck','Robert','You','Me') as $index=>$test){
    if($index==2)$user_id = '13311';
    if(!isset($array_increment[$user_id])){
        $array_increment[$user_id]=1;
    }

    $increment = $array_increment[$user_id];

    echo $user_id.'_'.$const.'_'.$increment.'<br />';
    $array_increment[$user_id]++;
}

Will show :

13310_userid_1
13310_userid_2
13311_userid_1
13311_userid_2

Answer 2

you could store the incremental value of each userid in a temporary session:

For each request check if $_GET['userid'] already exists in a session if not create it with value zero. Increment by one and use this value to create your string for inserting into DB

    //set up session if it is not already set


    if(!isset($_SESSION['users'][$_GET['userid'])){
    $_SESSION['users'][$_GET['userid']=0;
    }

    $_SESSION['users'][$_GET['userid']=$_SESSION['users'][$_GET['userid']+1;
    $user=$_GET['userid'].'_userid_'.$_SESSION['users'][$_GET['userid'];


   //insert $user into your DB or permanent storage.
   $db->insert($user);

Answer 3

(this should be a comment but its a bit verbose)

Your only makes sense if a database figures in here somewhere - but you never explicitly stated that this is the case nor which database it is.

Relational database design (and to quite a large extent, non-relational database design) is subject to the rules of normalization. These are methods for describing the structure of your data and prevent you doing stupid things. This breaks the first rule.

Assuming you were designing the system properly, then you would keep the three attributes as seperate fields. But that does not answer the question of whether the id is nominal, cardinal or ordinal (and in the case of ordinal numbers whether there is a requirement for them to be consecutive).