<?php

$arr = array(1, 2,3,4,5,3);

$uarr = array_unique($arr);

print_r($uarr);

echo "\\n";
echo "\n";

var_dump(array_diff($arr, array_diff($uarr, array_diff_assoc($arr, $uarr))));

echo "\n";
echo "<\n";
$unicos=(array_diff($arr, array_diff($uarr, array_diff_assoc($arr, $uarr))));

print_r($unicos);