- array_intersect_key: documentation ( source)
- print_r: documentation ( source)
- array_rand: documentation ( source)
- array_flip: documentation ( source)
<?php
$x = ["Alice", "Bob", "Carol", "Dan", "Eve", "Frank", "Grace", "Heidi"];
$k = 4;
$y = array_intersect_key($x, array_flip(array_rand($x, $k)));
print_r($y);