how to define array index dynamically?

Question

I have a PHP game which uses a MySQL table (history) that keeps track of users and how many times they knew the answer like:

username answer
-------- ------
user1    answer1
user2    answer2
user1    answer3

etc. And I want to use this table to print the best players, so I'm trying to implement an array like

public function getBestPlayers($hrows) /*history_rows*/
{
$ray=array();
$hlen = count($hrows);

for($i=0;$i<$hlen;$i++)
{
    $curnick = $hrows[$i]['knower'];
    $ray[$curnick]; //my attempt to "set" the index
    if($ray[$curnick]!=NULL)
    {
        $ray[$curnick]++;
    }
    else
    {
        $ray[$curnick]=1;
    }
}//for
$ray = sort($ray);
return $ray;
}//getBestPlayers()

so that in the end I have $ray['user1'] = 2 , $ray['user2'] = 1 etc. But this gives error "undefined index: user1". what should I do? thanks in advance..

You should check whether index is defined via isset() function before you even push a new item — Yang
– Yang, Commented Jan 14, 2013 at 0:31

Jon · Accepted Answer · 2013-01-14 00:34:11Z

3

You should let MySql do this for you, which will be much faster and much easier:

SELECT username, COUNT(*) AS score FROM tbl GROUP BY username ORDER BY score DESC

This will return a result set of the form

username score
-------- ------
user1    2
user2    1

answered Jan 14, 2013 at 0:34

Jon

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3 Comments

marvin Over a year ago

thanks, but I don't have scores. I have duplicates of user1, which I want to turn into scores dynamically, but don't want to store in mysql.

Jon Over a year ago

@marvin: I know. This query will do this automatically. Did you try to execute it?

marvin Over a year ago

OMG, this is great! I didn't know MySQL can do this. Thank you very much, and please forgive me for my ignorance :)

ilias · Accepted Answer · 2013-01-14 00:40:56Z

0

You ought to drop the $ray[$curnick]; line, as you can't (and shouldn't) try to declare array indices like that. Furthermore, you might want to replace if($ray[$curnick]!=NULL) by if(isset($ray[$curnick])) which will not try to access the array at that place but will merely check if it is set.

Other than that, your code would work, however, it would probably be a good idea to offload the collection of stats to the database.

answered Jan 14, 2013 at 0:40

ilias

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