I am trying to produce a HTML list grouped by "groupName" from the array below.

```
array (size=30)
  0 => 
    array (size=4)
      'groupOrder' => string '1' (length=1)
      'groupName' => string 'Class' (length=11)
      'txt' => string '............' (length=32)
      'ID' => string '6' (length=1)
  1 => 
    array (size=4)
      'groupOrder' => string '1' (length=1)
      'groupName' => string 'Size' (length=11)
      'txt' => string '..................' (length=34)
      'ID' => string '6' (length=1)
  2 => 
      ...

```

So I'd like produce something like this pseudo list:

* groupName
	+ txt
	+ txt
	+ txt
* next GroupName
	+ txt
	+ txt 
	...

So my code looks like this

```
foreach ($datafeed as $val => $row) {
       if (($datafeed[$val]['groupName']) == next($datafeed[$val]['groupName'])) {
           //same group - do nothing
       } else {
            echo $datafeed[$val]['groupName'];
       }

       echo "<li>".$row['txt']. "</li>";
}

```

But I'm getting errors about "next() expects parameter 1 to be array, string given".

I've tried all sorts of different syntax, but I'm not making much progress. How do I compare two values in a nested array?