What is a better way to get unique array Items based on key in PHP?

Question

I'm trying to achieve a set of unique array with my following function.

The Function:

/**
* uniqueAssocArray Removes arrys which have same keys
* @param Array $array Array to get unique items from
* @param String $uniqueKey the unique key 
* @return Array new array with unique items
* @author Junaid Qadir Baloch <[email protected]>
*/
function uniqueAssocArray($array, $uniqueKey) {
 if (!is_array($array)) {
 return array();
 }
 $uniqueKeys = array();
 foreach ($array as $key => $item) {
 if (!in_array($item[$uniqueKey], $uniqueKeys)) {
 $uniqueKeys[$item[$uniqueKey]] = $item;
 }
 }
 return $uniqueKeys;
}

Example Array:

$actualArray = array(
 user1 => array(
 'name' => 'User1',
 'age' => '25',
 'lastLogin' => '2013-08-16'
 ),
 user1 => array(
 'name' => 'User1',
 'age' => '25',
 'lastLogin' => '2013-08-10'
 ),
 user2 => array(
 'name' => 'User2',
 'age' => '35',
 'lastLogin' => '2013-08-08'
 ),
 user1 => array(
 'name' => 'User1',
 'age' => '25',
 'lastLogin' => '2013-07-10'
 )
);

I then call the function like so:

$resultArray = uniqueAssocArray($actualArray, 'name');

But...

I wonder is there a better way to do the same ?

Answer 1

Assuming your array is already sorted, you can just overwrite the values every time. Skip the inner if.

function uniqueAssocArray($array, $uniqueKey) {
 if (!is_array($array)) {
 return array();
 }
 $uniqueKeys = array();
 foreach ($array as $key => $item) {
 $groupBy=$item[$uniqueKey];
 if (isset( $uniqueKeys[$groupBy]))
 {
 //compare $item with $uniqueKeys[$groupBy] and decide if you 
 //want to use the new item
 $replace= ... 
 }
 else
 {
 $replace=true;
 }
 if ($replace) $uniqueKeys[$groupBy] = $item; 
 }
 return $uniqueKeys;
}

• Junaid Qadir Shekhanzai: Haha! i had already done the same but I have to accept your answer. There's one catch though, Array must be sorted in reverse order. and I test for existence for a key before I replace the values blindly.
• Junaid Qadir Shekhanzai: @mnhgI hope you won't mind if i un-accept your answer. I'm still looking for a better way
• mheinzerling: If you want the last element each, you need an ascending order. You are just overwriting the value again and again until you are on the last key.
• Junaid Qadir Shekhanzai: Yes, but what if the array is random?
• mheinzerling: If performance doesn't matter, sort it. If you want to handle this in the same loop just compare the current items key value with the already inserted.

Answer 2

Maybe you should try to use the function array_unique: http://php.net/manual/en/function.array-unique.php

If you prefer to go with your own solution, have a look at the method array_key_exists (http://www.php.net/manual/en/function.array-key-exists.php) to replace your condition:

if (!array_key_exists($key, $uniqueKeys)) {
 $uniqueKeys[$item[$uniqueKey]] = $item; 
}

A bit off-topic here, but you probably don't want to store a user's age but rather her birthday, to make sure it stays up-to-date.

• mheinzerling: If I get him right he wants to use the last not the first duplicate each.