preg_replace help remove duplicates ending with letter s

Im looking for a regular expression to remove duplicates from a list that end with the letter s. Thanks in advance!

The list BEFORE the duplicates are removed
dog
dogs
Necklace
Necklaces
Bracelet
Bracelets

The list AFTER the duplicates are removed
dog
Necklace
Bracelet

 

I think you will need to do it on two phases:
1. regexp:^(.*)({1})$
2. array_unique($array);

 

That works but only if its one word. How would i change your regexp to work with the example below?

The list BEFORE the duplicates are removed
dog bone
dog bones
14k Gold Necklace
14k Gold Necklaces
Gift Item Bracelet
Gift Item Bracelets

The list AFTER the duplicates are removed
dog bone
14k Gold Necklace
Gift Item Bracelet

 

Add \s inside the .*

 

Question,

1. what if you have only "dogs" in the list, not "dog" and "dogs".
Do you want to replace "dogs" into "dog" too?

2. What if there is "glass" in your list. Do you want the last "s" to be removed too ("glas")

 

No, in this case "dogs" would stay the same "dogs"
Im not asking how to remove 's' from the end of words

 

$items = file('file.txt');
$clean = array();

foreach($items as $item)
{
   $item = strtolower($item);
   if(empty($clean[$item]) && empty($clean["{$item}s"]) && empty($clean["{$item}es"]))
   {
      $clean[$item] = true;
   }
}

$items = array_keys($clean);
unset($clean);

print_r($items);

Code (markup):