May I ask the great God, php how do arrays remove duplicate values?

Ask the great God, how does the PHP array remove duplicate values???
Example

$array =array (1,2,3,3)

After the process of processing, once you know and repeat the data, delete,

Finally I need an array, because 3 repeats
------Solution--------------------
Array value 3 also don't?
------Solution--------------------
Array_unique () Ah
------Solution--------------------
$arr = Array (1,2,3,3);
$str = Implode (' ', $arr);
$arrres = Array_unique ($arr);
foreach ($arrres as $k = $v)
{
$num = Substr_count ($str, $v);
if ($num = = 1)
{
$res [] = $v;
}
}
Print_r ($res);
------Solution--------------------

$array = Array (1,2,3,3);
$t = Array_diff ($array,
  Array_keys (
    Array_filter (
      Array_count_values ($array), function ($v) {return $v >1;})
    )
  );
Print_r ($t);

Array
(
[0] = 1
[1] = 2
)

------Solution--------------------
References:

$arr = Array (1,2,3,3);
$str = Implode (' ', $arr);
$arrres = Array_unique ($arr);
foreach ($arrres as $k = $v)
{
$num = Substr_count ($str, $v);
if ($num = = 1)
{
$res [] = $v;
}
}
Print_r ($res);

Thank you for the idea, but the code seems to be simple: $arr = Array (1,2,3,3);
$str = Implode (' ', $arr);
foreach ($arr as $k = $v)
{
$num = Substr_count ($str, $v);
if ($num = = 1) {
$res [] = $v;
}
}
Print_r ($res);
?,
------Solution--------------------
Reference:

$array = Array (1,2,3,3);
$t = Array_diff ($array,
  Array_keys (
    Array_filter (
      Array_count_values ($array), function ($v) {return $v >1;})
    )
  );
Print_r ($t);

Array
(
[0] = 1
[1] = 2
)

Just like I thought.
------Solution--------------------
Just a little bit easier.

$array = Array (1,2,3,3);
$t = Array_diff ($array,
  Array_keys (
    Array_diff (
      Array_count_values ($array), array (1))
    )
  );
Print_r ($t);

------Solution--------------------
$array =array (1,2,3,3);
$a =array_count_values ($array);
$item =array ();
foreach ($a as $k = $v) if ($v ==1) $item []= $k;
Print_r ($item);

