- var_dump: documentation ( source)
- array_unique: documentation ( source)
- array_walk: documentation ( source)
<?php
$data = [[2,1], [1,2], [1,2], [2,1], [2,3], [3,2], [4,5]];
array_walk($data, 'sort');
$data = array_unique($data, SORT_REGULAR);
var_dump($data);