Undefined Offset 3 in array of 4 elements

Question

I have been playing with the Steam api and PHP the last couple days and all was well until I started receiving strange offset errors and duplicate values in my array. I tried breaking the code down into a version without api calls and html, but still receive the same unknown error.

I know that the key value is the same as the array element 1 (so I can use array_key_exists()). I like having all the elements in a single array for printing to html. The objective of the program is to make a fast accumulation of the data retrieved in json.

PHP Notice: Undefined offset: 3 in .../test.php on line 54
AKA This line -> games[$gameId][3] += 1

 $games=array();
 $i=10;
 while($i>0){
     $i--;
     $playtime = rand(1,1500);
     $twpt = rand(1,300);
     $gameId = rand(5,15);

     // clearly 4 elements in the array to use
     $newEntry = array($gameId, $playtime, $twpt, 1);

     if(array_key_exists($gameId, $games)){
         $games[$gameId] = array(
             //$games[$gameId][0] will not change
             $games[$gameId][1] += $newEntry[1],
             $games[$gameId][2] += $newEntry[2],
             $games[$gameId][3] += 1
         );
     } else {
         $games[$gameId] = $newEntry;
     }
 }

gen_Eric · Accepted Answer · 2014-02-19 17:34:20Z

1

The problem is when you are "updating" (re-setting) $games[$gameId][3].

$games[$gameId] = array(
    //$games[$gameId][0] will not change
    $games[$gameId][1] += $newEntry[1],
    $games[$gameId][2] += $newEntry[2],
    $games[$gameId][3] += 1
);

You are creating a new array, and are only adding 3 elements to it. You need to add $games[$gameId][0] to the new array, so that it will have 4 elements.

$games[$gameId] = array(
    $games[$gameId][0],
    $games[$gameId][1] += $newEntry[1],
    $games[$gameId][2] += $newEntry[2],
    $games[$gameId][3] += 1
);

Or, instead of making a new array every time, just simply do:

if(array_key_exists($gameId, $games)){
    $games[$gameId][1] += $newEntry[1];
    $games[$gameId][2] += $newEntry[2];
    $games[$gameId][3] += 1;
}
else {
     $games[$gameId] = $newEntry;
}

answered Feb 19, 2014 at 17:34

gen_Eric

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