$array = array(
array('group' => 'test', 'name' => 'Jane'),
array('group' => 'test', 'name' => 'John'),
array('group' => 'admin', 'name' => 'superadmin')
);
$unique_values_by_key = array_unique(array_column($array, 'group'));
<?php
$input = array("a" => "green", "red", "b" => "green", "blue", "red");
$result = array_unique($input);
print_r($result);
?>
<?php
// Syntax: array_unique(array $array, int $flags = SORT_STRING): array
// Desc: Removes duplicate values from an array
$arr = Array("red", "red", "green", "blue", "blue", "white");
echo "<pre>";
print_r($arr);
echo "</pre> <br><br>";
$arrUnique = array_unique($arr);
echo "<pre>";
print_r($arrUnique);
echo "</pre> <br><br>";
/* -------- output -----------
Array
(
[0] => red
[1] => red
[2] => green
[3] => blue
[4] => blue
[5] => white
)
Array
(
[0] => red
[2] => green
[3] => blue
[5] => white
)
*/
?>
$input = array_map("unserialize", array_unique(array_map("serialize", $input)));