trjhtr

I'm learning to code PHP and gave myself a challenge: Filter array data by matching a specific element value for duplication. I went through it logically on paper then wrote code and it worked on the first try :) But I bet it is the most inefficient way, so to learn I would like to compare it against what others would do. Below is my code. The array is just a few elements with keys like name and id. My result is a list of only items with unique ids from an array with many duplicate ids but different names.

Also, part of the challenge was testing XML, JSON, and Arrays so I made the original data XML and used SimpleXML but made a copy of that data as a PHP array and worked with that to do filtering (XPath challenge next).

Thanks for looking and any suggested improvements that I can learn from.

//$items is a SimpleXML array of items with name and id elements with many duplicate ids but different names.

//first iteration of id collection
$ids = array();
$countedIds = array();
//convert simplexml array $items to normal array (copy)
$itemsArray = json_decode(json_encode($items), TRUE); 
foreach ($itemsArray as $idItem) 

 //collection all ids
 $ids = $idItem['id']; 

//count number of each id and store in separate array
$countedIds = array_count_values($ids);
#print_r($countedIds);

//start cleaning out duplicates
foreach($itemsArray as $key => &$item)

 //clear any whitespace (thanks internets)
 #$thisid = trim($item->id); //if using simplexml
 $thisid = trim($item['id']);
 //check if this id is duplicated (multiple copies) in array
 if($countedIds[$thisid] >1)
 
 echo $thisid . "item has duplicates (" . $countedIds[$thisid] . ")<br />";
 //add found dupes to separate array
 $dupes = $thisid;
 //remove this item from $itemsArray and original $items simplexml array
 unset($itemsArray[$key]);
 unset($items[$key]);
 echo "removed element index " . $key . $item . "<br /><hr>"; 
 //remove this id from $ids array
 unset($ids[$key]);
 //clear out the counted ids
 unset($countedIds);
 //make a fresh array for counting ids
 $countedIds = array();
 //get updated id count
 $countedIds = array_count_values($ids);

 //test simplexml unset?
 #unset($sxe->$this->channel->item);
 
 
//review results
print_r($countedIds);
print_r($ids);
print_r($dupes);
print_r($itemsArray);
print_r($items);

If the sole purpose was to have a resultant array of objects that did not have a duplicated id then I would be tempted with the below:

// Indexes keyed by item id
$indexes = array();

// Cast to array of objects
$items = current((array)$items);

foreach ($items as $index => $item) 
 $id = ((array)$item)['id'];

 if (isset($indexes[$id])) 
 // Unset this item
 unset($items[$index]);
 // Unset the original instance
 unset($items[$indexes[$id]]);
 else 
 $indexes[$id] = $index;
 


// List names of items that doesn't have an id that is duplicated
foreach ($items as $item) 
 // Still have original SimpleXml object to work with
 echo $item->name . "n";