- print_r: documentation ( source)
- array_flip: documentation ( source)
- array_keys: documentation ( source)
<?php
$terms = ['one', 'two', 'three', 'one', 'four', 'five', 'two', 'six'];
// $output = array_unique($terms);
$output = array_keys(array_flip($terms));
print_r($output);