PHP Trouble with multidimensional Arrays

Question

I am currently attempting to extract data from a mysql DB and then place it into a multidimensional array, using the device name as a key.

The issue I'm having is that every time I iterate through the results the code im using kills the last item and replaces it.

Here is the code;

##sql connection##
$result = mysql_query(SELECT Device.DeviceID, Device.DeviceName, History.HistoryRec, History.HistoryDetectedDate from Device JOIN History ON Device.DeviceID=History.DeviceID WHERE History.Active_LastRound = 1 AND History.DetectedDate <= $hrs);
if (!$result){
die('invaild query:' . mysql_error());

while($row = mysql_fetch_array($result))
{
$last24hoursarray[$row['DeviceName']] = array($row['HistoryRec']);
}

So the issue i have is that my results set has multiple records with the same device name, and i cant work out how to put them into an array so that they do not overwrite the last item

for example i want

switch1 => issue1
switch1 => issue2
switch1 => issue3
switch2 => issue1
etc

but what i get is;

switch1 => issue3
switch2 => issue1

Thanks in advance. This is the first bit of PHP i have written, so please be gentle :D

It may not help answer your question, but you should stop using mysql_* functions. They're being deprecated. Instead use PDO (supported as of PHP 5.1) or mysqli (supported as of PHP 4.1). If you're not sure which one to use, read this article. — Matt
– Matt, Commented Aug 20, 2012 at 14:51
Why don't you just GROUP by Device Name and Sort by HistoryRec — Baba
– Baba, Commented Aug 20, 2012 at 14:53
Matt, thanks i didnt know those were going away, i guess im off to make those changes as well.... — Steve
– Steve, Commented Aug 20, 2012 at 15:09

Miroslav · Accepted Answer · 2012-08-20 14:52:25Z

5

PHP Array keys are unique, so you would not be able to store multiple values under the same key, try the following:

while($row = mysql_fetch_array($result)) {
        $last24hoursarray[$row['DeviceName']][] = $row['HistoryRec'];
}

answered Aug 20, 2012 at 14:52

Miroslav

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1 Comment

Steve Over a year ago

Ah didn't think of doing it this way... that works for what im doing.

codegen · Accepted Answer · 2012-08-20 15:06:22Z

2

First of all, arrays only allow a single value for keys. You will not be able to get.

switch1 => issue1
switch1 => issue2
switch1 => issue3

You can get

switch1 => [issue1, issue2, issue3]

I haven't taken the time to test the code, but it would be something like:

while($row = mysql_fetch_array($result)){
  if (array_key_exists ( $row['DeviceName'] , $last24hoursarray ){
    // append to existing issue.
    $last24hoursarray[$row['DeviceName']][] = array($row['HistoryRec']);
  } else{
    //No device name, create the array with issue.
    $last24hoursarray[$row['DeviceName']] = array($row['HistoryRec']);
  }
}

answered Aug 20, 2012 at 15:06

codegen

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Comments

Sebastian Breit · Accepted Answer · 2012-08-20 14:53:32Z

0

try creating a new array for each device:

$last24hoursarray[$row['DeviceName']] = new array($row['HistoryRec']);

answered Aug 20, 2012 at 14:53

Sebastian Breit

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Comments

Andrew · Accepted Answer · 2012-08-20 14:56:04Z

0

The reason that this code is not working is that PHP associative arrays only store one value per key of the array. This is so that you can lookup a unique value by key, which is the entire purpose of associative arrays. The code from Merca's example should work great, as it will create an array of values for each key in your associative array.

answered Aug 20, 2012 at 14:56

Andrew

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Comments

Ed Manet · Accepted Answer · 2012-08-20 14:57:42Z

0

It doesn't look like you're using a multi-dimensional array here. A multi-dimensional array is more like this:

switch1 = array(issue1, issue2, issue3);
switch2 = array(issue1);
multi = array(switch1, switch2);

issue = multi[0][1];  // issue2

answered Aug 20, 2012 at 14:57

Ed Manet

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