Synatx of array_unique
array array_unique(array array[, int sort_flags])
Creates and returns an array containing each element in the given array. If any values are duplicated, the later values are ignored. The sort_flags optional argument can be used to alter the sorting methods with constants: SORT_REGULAR, SORT_NUMERIC, SORT_STRING (default), and SORT_LOCALE_STRING. Keys from the original array are preserved
Example of array_unique in PHP
<?php
$input = array("a" => "green", "red", "b" => "green", "blue", "red");
$result = array_unique($input);
print_r($result);
?>
Output
Array ( [a] => green [0] => red [1] => blue )